CINXE.COM

<!DOCTYPE html> <html lang="en" class="no-js"> <head> <meta charset="UTF-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="applicable-device" content="pc,mobile"> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta name="robots" content="max-image-preview:large"> <meta name="access" content="Yes"> <meta name="360-site-verification" content="1268d79b5e96aecf3ff2a7dac04ad990" /> <title>On the position of helium and neon in the Periodic Table of Elements | Foundations of Chemistry</title> <meta name="twitter:site" content="@SpringerLink"/> <meta name="twitter:card" content="summary_large_image"/> <meta name="twitter:image:alt" content="Content cover image"/> <meta name="twitter:title" content="On the position of helium and neon in the Periodic Table of Elements"/> <meta name="twitter:description" content="Foundations of Chemistry - Helium and neon, the two lightest noble gases, have been traditionally positioned by IUPAC in the Group 18 of the Periodic Table of Elements, together with argon, and..."/> <meta name="twitter:image" content="https://static-content.springer.com/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig1_HTML.gif"/> <meta name="journal_id" content="10698"/> <meta name="dc.title" content="On the position of helium and neon in the Periodic Table of Elements"/> <meta name="dc.source" content="Foundations of Chemistry 2017 20:3"/> <meta name="dc.format" content="text/html"/> <meta name="dc.publisher" content="Springer"/> <meta name="dc.date" content="2017-11-01"/> <meta name="dc.type" content="OriginalPaper"/> <meta name="dc.language" content="En"/> <meta name="dc.copyright" content="2017 The Author(s)"/> <meta name="dc.rights" content="2017 The Author(s)"/> <meta name="dc.rightsAgent" content="journalpermissions@springernature.com"/> <meta name="dc.description" content="Helium and neon, the two lightest noble gases, have been traditionally positioned by IUPAC in the Group 18 of the Periodic Table of Elements, together with argon, and other unreactive or moderately reactive gaseous elements (krypton, xenon, radon), and oganesson. In this account we revive the old discussion on the possible placement of helium in the Group 2, while preserving the position of neon in Group 18. We provide quantum-chemical arguments for such scenario—as well as other qualitative and quantitative arguments—and we describe previous suggestions in the literature which support it or put it into question. To this author’s own taste, He should be placed in Group 2."/> <meta name="prism.issn" content="1572-8463"/> <meta name="prism.publicationName" content="Foundations of Chemistry"/> <meta name="prism.publicationDate" content="2017-11-01"/> <meta name="prism.volume" content="20"/> <meta name="prism.number" content="3"/> <meta name="prism.section" content="OriginalPaper"/> <meta name="prism.startingPage" content="191"/> <meta name="prism.endingPage" content="207"/> <meta name="prism.copyright" content="2017 The Author(s)"/> <meta name="prism.rightsAgent" content="journalpermissions@springernature.com"/> <meta name="prism.url" content="https://link.springer.com/article/10.1007/s10698-017-9302-7"/> <meta name="prism.doi" content="doi:10.1007/s10698-017-9302-7"/> <meta name="citation_pdf_url" content="https://link.springer.com/content/pdf/10.1007/s10698-017-9302-7.pdf"/> <meta name="citation_fulltext_html_url" content="https://link.springer.com/article/10.1007/s10698-017-9302-7"/> <meta name="citation_journal_title" content="Foundations of Chemistry"/> <meta name="citation_journal_abbrev" content="Found Chem"/> <meta name="citation_publisher" content="Springer Netherlands"/> <meta name="citation_issn" content="1572-8463"/> <meta name="citation_title" content="On the position of helium and neon in the Periodic Table of Elements"/> <meta name="citation_volume" content="20"/> <meta name="citation_issue" content="3"/> <meta name="citation_publication_date" content="2018/10"/> <meta name="citation_online_date" content="2017/11/01"/> <meta name="citation_firstpage" content="191"/> <meta name="citation_lastpage" content="207"/> <meta name="citation_article_type" content="Article"/> <meta name="citation_fulltext_world_readable" content=""/> <meta name="citation_language" content="en"/> <meta name="dc.identifier" content="doi:10.1007/s10698-017-9302-7"/> <meta name="DOI" content="10.1007/s10698-017-9302-7"/> <meta name="size" content="201400"/> <meta name="citation_doi" content="10.1007/s10698-017-9302-7"/> <meta name="citation_springer_api_url" content="http://api.springer.com/xmldata/jats?q=doi:10.1007/s10698-017-9302-7&api_key="/> <meta name="description" content="Helium and neon, the two lightest noble gases, have been traditionally positioned by IUPAC in the Group 18 of the Periodic Table of Elements, together with"/> <meta name="dc.creator" content="Grochala, Wojciech"/> <meta name="dc.subject" content="Philosophy of Science"/> <meta name="dc.subject" content="Chemistry/Food Science, general"/> <meta name="dc.subject" content="History, general"/> <meta name="dc.subject" content="Physical Chemistry"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. A; citation_title=Stable compounds of the lightest noble gases: a computational investigation of RNBeNg (Ng = He, Ne, Ar); citation_author=P Antoniotti, N Bronzolino, F Grandinetti; citation_volume=107; citation_issue=16; citation_publication_date=2003; citation_pages=2974-2980; citation_doi=10.1021/jp027760b; citation_id=CR1"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. A; citation_title=Noble gas anions: a theoretical investigation of FNgBN− (Ng = He–Xe); citation_author=P Antoniotti, S Borocci, N Bronzolino, P Cecchi, F Grandinetti; citation_volume=111; citation_issue=40; citation_publication_date=2007; citation_pages=10144-10151; citation_doi=10.1021/jp0743673; citation_id=CR2"/> <meta name="citation_reference" content="citation_journal_title=Proc. Chem. Soc. Lond. Chem. Soc.; citation_title=Xenon hexafluoroplatinate (V) Xe+[PtF6]− ; citation_author=N Bartlett; citation_volume=6; citation_publication_date=1962; citation_pages=218; citation_id=CR3"/> <meta name="citation_reference" content="citation_journal_title=J. Fluor. Chem.; citation_title=Redox reactions in the XeF2/platinum fluoride and XeF2/palladium fluoride systems and the conversion of XeF2 to XeF4 and Xe; citation_author=N Bartlett, B Žemva, L Graham; citation_volume=7; citation_issue=1–3; citation_publication_date=1976; citation_pages=301-320; citation_doi=10.1016/S0022-1139(00)84003-8; citation_id=CR4"/> <meta name="citation_reference" content="citation_journal_title=Nature; citation_title=Helium can form stable bonds; citation_author=N Bartlett; citation_volume=331; citation_publication_date=1998; citation_pages=487-488; citation_doi=10.1038/331487a0; citation_id=CR5"/> <meta name="citation_reference" content="citation_journal_title=J. Am. Chem. Soc.; citation_title=The chemical bond between Au(I) and the noble gases. Comparative study of NgAuF and NgAu+ (Ng = Ar, Kr, Xe) by density functional and coupled cluster methods; citation_author=L Belpassi, I Infante, F Tarantelli, L Visscher; citation_volume=130; citation_issue=3; citation_publication_date=2008; citation_pages=1048-1060; citation_doi=10.1021/ja0772647; citation_id=CR6"/> <meta name="citation_reference" content="citation_title=New ideas in chemistry from fresh energy for the periodic law; citation_publication_date=2006; citation_id=CR7; citation_author=H Bent; citation_publisher=AuthorHouse"/> <meta name="citation_reference" content="citation_journal_title=J. Chem. Phys.; citation_title=Stability of a chemically bound helium compound in high-pressure solid helium; citation_author=Z Bihary, GM Chaban, RB Gerber; citation_volume=117; citation_issue=11; citation_publication_date=2002; citation_pages=5105-5108; citation_doi=10.1063/1.1506150; citation_id=CR8"/> <meta name="citation_reference" content="citation_journal_title=Chem. Phys. Lett.; citation_title=Noble gas–sulfur anions: a theoretical investigation of FNgS − (Ng = He, Ar, Kr, Xe); citation_author=S Borocci, N Bronzolino, F Grandinetti; citation_volume=458; citation_issue=1–3; citation_publication_date=2008; citation_pages=48-53; citation_doi=10.1016/j.cplett.2008.04.098; citation_id=CR9"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. A; citation_title=Cationic noble gas hydrides: a theoretical investigation of dinuclear HNgFNgH+ (Ng = He − Xe); citation_author=S Borocci, N Bronzolino, M Giordani, F Grandinetti; citation_volume=114; citation_issue=27; citation_publication_date=2010; citation_pages=7382-7390; citation_doi=10.1021/jp102018n; citation_id=CR10"/> <meta name="citation_reference" content="Brock, D. S., Schrobilgen, G. J., Žemva, B.: Noble-gas chemistry. In: Reedijk, J., Poeppelmeier, K. (eds.) Comprehensive Inorganic Chemistry II (Second Edition): From Elements to Applications, vol. 1, pp. 755–822 (2013). http://www.sciencedirect.com/science/referenceworks/9780080965291 "/> <meta name="citation_reference" content="citation_journal_title=Chem. Eur. J.; citation_title=Experimental evidence of chemical components in the bonding of helium and neon with neutral molecules; citation_author=D Cappelletti, A Bartocci, F Grandinetti, S Falcinelli, L Belpassi, F Tarantelli, F Pirani; citation_volume=21; citation_issue=16; citation_publication_date=2015; citation_pages=6234-6240; citation_doi=10.1002/chem.201406103; citation_id=CR12"/> <meta name="citation_reference" content="citation_journal_title=Inorg. Chem.; citation_title=Perfluorammonium and alkali-metal salts of the heptafluoroxenon(VI) and octafluoroxenon(VI) anions; citation_author=KO Christe, WW Wilson; citation_volume=21; citation_issue=12; citation_publication_date=1982; citation_pages=4113-4117; citation_doi=10.1021/ic00142a001; citation_id=CR13"/> <meta name="citation_reference" content="citation_journal_title=J. Am. Chem. Soc.; citation_title=The pentafluoroxenate(IV) anion, XeF5 −: the first example of a pentagonal planar AX5 species; citation_author=KO Christe, EC Curtis, DA Dixon, HP Mercier, JCP Sanders, GJ Schrobilgen; citation_volume=113; citation_issue=9; citation_publication_date=1991; citation_pages=3351-3361; citation_doi=10.1021/ja00009a021; citation_id=CR14"/> <meta name="citation_reference" content="citation_journal_title=Angew. Chem. Int. Ed. Engl.; citation_title=A renaissance in noble gas chemistry; citation_author=KO Christe; citation_volume=40; citation_issue=8; citation_publication_date=2001; citation_pages=1419-1421; citation_doi=10.1002/1521-3773(20010417)40:8<1419::AID-ANIE1419>3.0.CO;2-J; citation_id=CR15"/> <meta name="citation_reference" content="citation_journal_title=Inorg. Chem.; citation_title=Third row transition metal hexafluorides, extraordinary oxidizers, and Lewis acids: electron affinities, fluoride affinities, and heats of formation of WF6, ReF6, OsF6, IrF6, PtF6, and AuF6 ; citation_author=R Craciun, D Picone, RT Long, S Li, DA Dixon, KA Peterson, KO Christe; citation_volume=49; citation_issue=3; citation_publication_date=2010; citation_pages=1056-1070; citation_doi=10.1021/ic901967h; citation_id=CR16"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. A; citation_title=Bonding of rare-gas atoms to Si in reactions of rare gases with SiF3 + ; citation_author=A Cunje, VI Baranov, Y Ling, AC Hopkinson, DK Bohme; citation_volume=105; citation_issue=49; citation_publication_date=2001; citation_pages=11073-11079; citation_doi=10.1021/jp011908u; citation_id=CR17"/> <meta name="citation_reference" content="citation_journal_title=Nat. Chem.; citation_title=Synthesis and stability of xenon oxides Xe2O5 and Xe3O2 under pressure; citation_author=A Dewaele, N Worth, CJ Pickard, RJ Needs, S Pascarelli, O Mathon, M Mezouar, T Irifune; citation_volume=8; citation_issue=8; citation_publication_date=2016; citation_pages=784-790; citation_doi=10.1038/nchem.2528; citation_id=CR18"/> <meta name="citation_reference" content="citation_journal_title=Inorg. Chem.; citation_title=Heats of formation of krypton fluorides and stability predictions for KrF4 and KrF6 from high level electronic structure calculations; citation_author=DA Dixon, TH Wang, DJ Grant, KA Peterson, KO Christe, GJ Schrobilgen; citation_volume=46; citation_issue=23; citation_publication_date=2007; citation_pages=10016-10021; citation_doi=10.1021/ic701313h; citation_id=CR19"/> <meta name="citation_reference" content="citation_journal_title=Nat. Chem.; citation_title=Stable compound of helium and sodium at high pressure; citation_author=X Dong, AR Oganov, AF Goncharov, E Stavrou, S Lobanov, G Saleh, G-R Qian, Q Zhu, C Gatti, VL Deringer, R Dronskowski, X-F Zhou, V Prakapenka, Z Konôpková, IA Popov, AI Boldyrev, H-T Wang; citation_volume=9; citation_publication_date=2017; citation_pages=440-445; citation_doi=10.1038/nchem.2716; citation_id=CR20"/> <meta name="citation_reference" content="citation_journal_title=J. Chem. Phys.; citation_title=The microwave spectra and structures of Ar–AgX (X = F, Cl, Br); citation_author=CJ Evans, MCL Gerry; citation_volume=112; citation_issue=3; citation_publication_date=2000; citation_pages=1321-1329; citation_doi=10.1063/1.480684; citation_id=CR21"/> <meta name="citation_reference" content="citation_journal_title=Nat. Chem.; citation_title=Table manners; citation_author=M Francl; citation_volume=1; citation_issue=2; citation_publication_date=2009; citation_pages=97-98; citation_doi=10.1038/nchem.183; citation_id=CR22"/> <meta name="citation_reference" content="citation_journal_title=Struct. Bonding; citation_title=The chemistry of the noble gas elements helium, neon, and argon—experimental facts and theoretical predictions; citation_author=G Frenking, D Cremer; citation_volume=73; citation_publication_date=1990; citation_pages=17; citation_doi=10.1007/3-540-52124-0_2; citation_id=CR25"/> <meta name="citation_reference" content="citation_journal_title=J. Am. Chem. Soc.; citation_title=Stabilities and nature of the attractive interactions in HeBeO, NeBeO, and ArBeO and a comparison with analogs NGLiF, NGBN, and NGLiH (NG = He, Ar). A theoretical investigation; citation_author=G Frenking, W Koch, J Gauss, D Cremer; citation_volume=110; citation_issue=24; citation_publication_date=1988; citation_pages=8007-8016; citation_doi=10.1021/ja00232a009; citation_id=CR23"/> <meta name="citation_reference" content="citation_journal_title=J. Am. Chem. Soc.; citation_title=The ArF+ cation. Is it stable enough to be isolated in a salt?; citation_author=G Frenking, W Koch, CA Deakyne, JF Liebman, N Bartlett; citation_volume=111; citation_issue=1; citation_publication_date=1989; citation_pages=31-33; citation_doi=10.1021/ja00183a005; citation_id=CR24"/> <meta name="citation_reference" content="citation_journal_title=J. Am. Chem. Soc.; citation_title=Light noble-gas chemistry - structures, stabilities, and bonding of helium, neon and argon compounds; citation_author=G Frenking, W Koch, F Reichel, D Cremer; citation_volume=112; citation_issue=11; citation_publication_date=1988; citation_pages=4240-4256; citation_doi=10.1021/ja00167a020; citation_id=CR200"/> <meta name="citation_reference" content="citation_journal_title=J. Chem. Soc. Chem. Commun.; citation_title=The pentafluorophenylxenon(II) cation: [C6F5Xe]+; the first stable system with a xenon–carbon bond; citation_author=HJ Frohn, S Jakobs; citation_volume=10; citation_publication_date=1989; citation_pages=625-627; citation_doi=10.1039/C39890000625; citation_id=CR26"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. A; citation_title=The noble gases: how their electronegativity and hardness determines their chemistry; citation_author=J Furtado, F Proft, P Geerlings; citation_volume=119; citation_publication_date=2015; citation_pages=1339-1346; citation_doi=10.1021/jp5098876; citation_id=CR27"/> <meta name="citation_reference" content="citation_journal_title=Coord. Chem. Rev.; citation_title=The octet rule and hypervalence: two misunderstood concepts; citation_author=RJ Gillespie, B Silvi; citation_volume=233–234; citation_publication_date=2002; citation_pages=53-62; citation_doi=10.1016/S0010-8545(02)00102-9; citation_id=CR28"/> <meta name="citation_reference" content="citation_journal_title=Chem. Eur. J.; citation_title=Stabilization of HHeF by complexation: is it a really viable strategy?; citation_author=M Giordani, P Antoniotti, F Grandinetti; citation_volume=16; citation_issue=21; citation_publication_date=2010; citation_pages=6257-6264; citation_doi=10.1002/chem.200903282; citation_id=CR29"/> <meta name="citation_reference" content="citation_journal_title=Pol. J. Chem.; citation_title=Morphological classification of chemical structural units; citation_author=AW Górski; citation_volume=75; citation_publication_date=2001; citation_pages=159-207; citation_id=CR30"/> <meta name="citation_reference" content="citation_journal_title=Coord. Chem. Rev.; citation_title=Concerning the nature of XePtF6 ; citation_author=L Graham, O Graudejus, NK Jha, N Bartlett; citation_volume=197; citation_issue=1; citation_publication_date=2000; citation_pages=321-334; citation_doi=10.1016/S0010-8545(99)00190-3; citation_id=CR31"/> <meta name="citation_reference" content="citation_journal_title=Nat. Chem.; citation_title=Neon behind the signs; citation_author=F Grandinetti; citation_volume=5; citation_issue=5; citation_publication_date=2013; citation_pages=438; citation_doi=10.1038/nchem.1631; citation_id=CR32"/> <meta name="citation_reference" content="citation_journal_title=Chem. Soc. Rev.; citation_title=Atypical compounds of gases, which have been called ‘noble’; citation_author=W Grochala; citation_volume=36; citation_issue=10; citation_publication_date=2007; citation_pages=1632-1655; citation_doi=10.1039/b702109g; citation_id=CR33"/> <meta name="citation_reference" content="citation_journal_title=Pol. J. Chem.; citation_title=On chemical bonding between helium and oxygen; citation_author=W Grochala; citation_volume=83; citation_issue=1; citation_publication_date=2009; citation_pages=87-122; citation_id=CR34"/> <meta name="citation_reference" content="Grochala, W.: Quo vadis noble gas chemistry? Talk at Universita de la Tuscia, Viterbo, Jun 9 (2009b)"/> <meta name="citation_reference" content="citation_title=Noble gas chemistry; citation_inbook_title=Physics and Chemistry at Low Temperatures; citation_publication_date=2011; citation_pages=421-448; citation_id=CR36; citation_author=W Grochala; citation_author=L Khriachtchev; citation_author=M Räsänen; citation_publisher=Pan Stanford Publishing"/> <meta name="citation_reference" content="citation_journal_title=Phys. Chem. Chem. Phys.; citation_title=Metastable He–O bond inside a ferroelectric molecular cavity: (HeO)(LiF)2 ; citation_author=W Grochala; citation_volume=14; citation_publication_date=2012; citation_pages=14860-14868; citation_doi=10.1039/c2cp42321a; citation_id=CR37"/> <meta name="citation_reference" content="citation_title=Can elemental helium form chemical bonds in neutral molecules? Wissenschaftsforum Chemie 2013; citation_publication_date=2013; citation_id=CR38; citation_author=W Grochala; citation_publisher=Darmstadt"/> <meta name="citation_reference" content="Grochala, W.: Unpublished periodic DFT results (2014)"/> <meta name="citation_reference" content="citation_journal_title=Chem. Rev.; citation_title=The chemistry of xenon(IV); citation_author=J Haner, GJ Schrobilgen; citation_volume=115; citation_issue=2; citation_publication_date=2015; citation_pages=1255-1295; citation_doi=10.1021/cr500427p; citation_id=CR40"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. Lett.; citation_title=Xenon suboxides stable under pressure; citation_author=A Hermann, P Schwerdtfeger; citation_volume=5; citation_issue=24; citation_publication_date=2014; citation_pages=4336-4342; citation_doi=10.1021/jz502230b; citation_id=CR41"/> <meta name="citation_reference" content="citation_journal_title=Coord. Chem. Rev.; citation_title=Coordination chemistry of the noble gases and noble gas fluorides; citation_author=EG Hope; citation_volume=257; citation_issue=5–6; citation_publication_date=2013; citation_pages=902-909; citation_doi=10.1016/j.ccr.2012.07.017; citation_id=CR42"/> <meta name="citation_reference" content="citation_journal_title=Angew. Chem. Int. Ed.; citation_title=Gold(I) and Mercury(II) Xenon Complexes; citation_author=IC Hwang, S Seidel, K Seppelt; citation_volume=42; citation_issue=36; citation_publication_date=2003; citation_pages=4392-4395; citation_doi=10.1002/anie.200351208; citation_id=CR43"/> <meta name="citation_reference" content="citation_title=Essais de classification hélicoïdale des éléments chimiques; citation_publication_date=1928; citation_id=CR44; citation_author=C Janet; citation_publisher=Imprimerie Départementale de l’Oise"/> <meta name="citation_reference" content="citation_title=La classification hélicoïdale des éléments chimiques; citation_publication_date=1928; citation_id=CR45; citation_author=C Janet; citation_publisher=Imprimerie Départementale de l’Oise"/> <meta name="citation_reference" content="citation_journal_title=Chem. News; citation_title=The helicoidal classification of the elements; citation_author=C Janet; citation_volume=138; citation_issue=372–374; citation_publication_date=1929; citation_pages=388-393; citation_id=CR46"/> <meta name="citation_reference" content="citation_journal_title=Nature; citation_title=A stable argon compound; citation_author=L Khriachtchev, M Pettersson, N Runeberg, J Lundell, M Räsänen; citation_volume=406; citation_publication_date=2000; citation_pages=874-876; citation_doi=10.1038/35022551; citation_id=CR47"/> <meta name="citation_reference" content="citation_journal_title=Nat. Chem.; citation_title=Two- and three-dimensional extended solids and metallization of compressed XeF2 ; citation_author=M Kim, M Debessai, C-S Yoo; citation_volume=2; citation_issue=9; citation_publication_date=2010; citation_pages=784-788; citation_doi=10.1038/nchem.724; citation_id=CR48"/> <meta name="citation_reference" content="citation_journal_title=Chem. Phys. Lett.; citation_title=Are there neutral helium compounds which are stable in their ground state? A theoretical investigation of HeBCH and HeBeO; citation_author=W Koch, JR Collins, G Frenking; citation_volume=132; citation_issue=3; citation_publication_date=1986; citation_pages=330-333; citation_doi=10.1016/0009-2614(86)80134-8; citation_id=CR49"/> <meta name="citation_reference" content="citation_journal_title=Inorg. Chem.; citation_title=Freezing in resonance structures for better packing: XeF2 becomes (XeF+)(F−) at large compression; citation_author=D Kurzydłowski, P Zaleski-Ejgierd, W Grochala, R Hoffmann; citation_volume=50; citation_issue=8; citation_publication_date=2011; citation_pages=3832-3840; citation_doi=10.1021/ic200371a; citation_id=CR50"/> <meta name="citation_reference" content="citation_journal_title=Phys. Chem. Chem. Phys.; citation_title=High-pressure stabilization of argon fluorides; citation_author=D Kurzydłowski, P Zaleski-Ejgierd; citation_volume=18; citation_issue=4; citation_publication_date=2016; citation_pages=2309-2313; citation_doi=10.1039/C5CP05725F; citation_id=CR51"/> <meta name="citation_reference" content="citation_journal_title=Angew. Chem. Int. Ed. Engl.; citation_title=One or several pioneers? The discovery of noble-gas compounds; citation_author=P Laszlo, GJ Schrobilgen; citation_volume=27; citation_issue=4; citation_publication_date=1988; citation_pages=479-489; citation_doi=10.1002/anie.198804791; citation_id=CR52"/> <meta name="citation_reference" content="Le Cornec, H.: The distribution of atomic ionization potentials reveals an unexpected Periodic Table. physchem/0201007 (2002)"/> <meta name="citation_reference" content="citation_journal_title=Coord. Chem. Rev.; citation_title=The chemistry of krypton; citation_author=JF Lehmann, HPA Mercier, GJ Schrobilgen; citation_volume=233–234; citation_publication_date=2002; citation_pages=1-39; citation_doi=10.1016/S0010-8545(02)00202-3; citation_id=CR54"/> <meta name="citation_reference" content="citation_title=Modeling Marvels: Computational Anticipation of Novel Molecules, Chapter 5; citation_publication_date=2008; citation_id=CR55; citation_author=EG Lewars; citation_publisher=Springer"/> <meta name="citation_reference" content="citation_journal_title=J. Am. Chem. Soc.; citation_title=The atom and the molecule; citation_author=GN Lewis; citation_volume=38; citation_issue=4; citation_publication_date=1916; citation_pages=762-785; citation_doi=10.1021/ja02261a002; citation_id=CR56"/> <meta name="citation_reference" content="citation_title=Valence and the structure of atoms and molecules; citation_publication_date=1923; citation_id=CR57; citation_author=GN Lewis; citation_publisher=Chemical Catalog"/> <meta name="citation_reference" content="citation_journal_title=J. Am. Chem. Soc.; citation_title=Theoretical prediction of noble gas containing anions FNgO− (Ng = He, Ar, and Kr); citation_author=T-H Li, C-H Mou, H-R Chen, W-P Hu; citation_volume=127; citation_issue=25; citation_publication_date=2005; citation_pages=9241-9245; citation_doi=10.1021/ja051276f; citation_id=CR58"/> <meta name="citation_reference" content="citation_journal_title=Sci. Rep.; citation_title=Stable lithium argon compounds under high pressure; citation_author=X Li, A Hermann, F Peng, J Lv, Y Wang, H Wang, Y Ma; citation_volume=5; citation_publication_date=2015; citation_pages=16675; citation_doi=10.1038/srep16675; citation_id=CR59"/> <meta name="citation_reference" content="citation_journal_title=J. Am. Chem. Soc.; citation_title=A salt chemistry of light noble gas compounds; citation_author=JF Liebman, LC Allen; citation_volume=92; citation_issue=12; citation_publication_date=1970; citation_pages=3539-3543; citation_doi=10.1021/ja00715a002; citation_id=CR60"/> <meta name="citation_reference" content="citation_journal_title=Struct. Chem.; citation_title=Theoretical investigation of the noble gas molecular anions XAuNgX− and HAuNgX− (X = F, Cl, Br; Ng = Xe, Kr, Ar); citation_author=G Liu, Y Zhang, X Bai, F He, X Zhang, Z Wang, W Zhang; citation_volume=23; citation_issue=6; citation_publication_date=2012; citation_pages=1693-1710; citation_doi=10.1007/s11224-012-9978-1; citation_id=CR61"/> <meta name="citation_reference" content="citation_journal_title=Chem. Phys. Lett.; citation_title=Theoretical study on the noble-gas anions F−(NgO)n (Ng = He, Ar, and Kr); citation_author=Y-L Liu, Y-H Chang, T-H Li, H-R Chen, W-P Hu; citation_volume=439; citation_issue=1–3; citation_publication_date=2007; citation_pages=14-17; citation_doi=10.1016/j.cplett.2007.03.045; citation_id=CR62"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. Lett.; citation_title=Generation of the ArCF2 2+ dication; citation_author=JF Lockyear, K Douglas, SD Price, M Karwowska, KJ Fijałkowski, W Grochala, M Remeš, J Roithová, D Schröder; citation_volume=1; citation_issue=1; citation_publication_date=2010; citation_pages=358-362; citation_doi=10.1021/jz900274p; citation_id=CR63"/> <meta name="citation_reference" content="citation_journal_title=Chem. Phys. Lett.; citation_title=Transition metal-noble gas bonding: the next frontier; citation_author=CC Lovallo, M Kłobukowski; citation_volume=368; citation_issue=5; citation_publication_date=2003; citation_pages=589-593; citation_doi=10.1016/S0009-2614(02)01913-9; citation_id=CR64"/> <meta name="citation_reference" content="citation_journal_title=Chem. Phys. Lett.; citation_title=Combined ab initio and anharmonic vibrational spectroscopy calculations for rare gas containing fluorohydrides, HRgF; citation_author=J Lundell, GM Chaban, RB Gerber; citation_volume=331; citation_issue=2–4; citation_publication_date=2000; citation_pages=308-316; citation_doi=10.1016/S0009-2614(00)01180-5; citation_id=CR65"/> <meta name="citation_reference" content="citation_journal_title=Chem. Phys. Lett.; citation_title=Are H–He–Cl and H–Ne–Cl metastable species? A computational study; citation_author=SAC McDowell; citation_volume=342; citation_issue=5–6; citation_publication_date=2001; citation_pages=631-635; citation_doi=10.1016/S0009-2614(01)00634-0; citation_id=CR66"/> <meta name="citation_reference" content="citation_journal_title=Nat. Chem.; citation_title=React with nobility; citation_author=M Miao; citation_volume=9; citation_publication_date=2017; citation_pages=409-410; citation_doi=10.1038/nchem.2768; citation_id=CR67"/> <meta name="citation_reference" content="citation_journal_title=J. Chem. Soc. Chem. Commun.; citation_title=The first compound with a stable xenon-carbon bond: 19F- and 129Xe-n.m.r. spectroscopic evidence for pentafluorophenylxenon(II) fluoroborates; citation_author=D Naumann, W Tyrra; citation_volume=1; citation_publication_date=1989; citation_pages=47-50; citation_doi=10.1039/c39890000047; citation_id=CR68"/> <meta name="citation_reference" content="citation_journal_title=Found. Chem.; citation_title=On the rightful place for He within the periodic table; citation_author=O Novaro; citation_volume=10; citation_publication_date=2008; citation_pages=3-12; citation_doi=10.1007/s10698-007-9041-2; citation_id=CR69"/> <meta name="citation_reference" content="citation_journal_title=J. Comput. Chem.; citation_title=Structure and stability of noble gas bound EX3 + compounds (E = C, Ge, Sn, Pb; X = H, F, Cl, Br); citation_author=S Pan, D Moreno, S Ghosh, PK Chattaraj, G Merino; citation_volume=37; citation_issue=2; citation_publication_date=2016; citation_pages=226-236; citation_doi=10.1002/jcc.23986; citation_id=CR70"/> <meta name="citation_reference" content="Pichon, A.: A letter about ‘Neon behind the signs’. Nature Chemistry blog “The Sceptical Chymist” (2013). http://blogs.nature.com/thescepticalchymist/2013/12/a-letter-about-neon-behind-the-signs.html "/> <meta name="citation_reference" content="citation_journal_title=Chem. Rev.; citation_title=The physics behind chemistry, and the Periodic Table; citation_author=P Pyykkö; citation_volume=112; citation_issue=1; citation_publication_date=2012; citation_pages=371-384; citation_doi=10.1021/cr200042e; citation_id=CR72"/> <meta name="citation_reference" content="citation_journal_title=Phys. Chem. Chem. Phys.; citation_title=A suggested periodic table up to Z ≤ 172, based on Dirac-Fock calculations on atoms and ions; citation_author=P Pyykkö; citation_volume=13; citation_issue=1; citation_publication_date=2011; citation_pages=161-168; citation_doi=10.1039/C0CP01575J; citation_id=CR73"/> <meta name="citation_reference" content="citation_journal_title=Science; citation_title=Noble gases; citation_author=E Renouf; citation_volume=13; citation_issue=320; citation_publication_date=1901; citation_pages=268-270; citation_doi=10.1126/science.13.320.268; citation_id=CR74"/> <meta name="citation_reference" content="citation_journal_title=Angew. Chem. Int. Ed.; citation_title=Silicon compounds of Neon and Argon; citation_author=J Roithová, D Schröder; citation_volume=48; citation_issue=46; citation_publication_date=2009; citation_pages=8788-8790; citation_doi=10.1002/anie.200903706; citation_id=CR75"/> <meta name="citation_reference" content="citation_journal_title=Nat. Chem.; citation_title=The rational design of helium bonds; citation_author=H Rzepa; citation_volume=2; citation_issue=5; citation_publication_date=2010; citation_pages=390-393; citation_doi=10.1038/nchem.596; citation_id=CR76"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. Lett.; citation_title=Prediction of superhalogen-stabilized noble gas compounds; citation_author=D Samanta; citation_volume=5; citation_issue=18; citation_publication_date=2014; citation_pages=3151-3156; citation_doi=10.1021/jz501404h; citation_id=CR77"/> <meta name="citation_reference" content="citation_journal_title=Educ. Chem.; citation_title=Presenting the left-step periodic table; citation_author=ER Scerri; citation_volume=42; citation_publication_date=2005; citation_pages=135-136; citation_id=CR78"/> <meta name="citation_reference" content="citation_journal_title=HYLE-Int. J. Phil. Chem.; citation_title=Some aspects of the metaphysics of chemistry and the nature of the elements; citation_author=E Scerri; citation_volume=11; citation_publication_date=2005; citation_pages=127-145; citation_id=CR79"/> <meta name="citation_reference" content="citation_title=The Periodic Table: Its Story and Its Significance; citation_publication_date=2007; citation_id=CR80; citation_author=ER Scerri; citation_publisher=Oxford University Press"/> <meta name="citation_reference" content="citation_journal_title=Chem. World; citation_title=Periodic change; citation_author=ER Scerri; citation_volume=3; citation_publication_date=2009; citation_pages=46-49; citation_id=CR81"/> <meta name="citation_reference" content="citation_journal_title=J. Chem. Educ.; citation_title=Prospects for further considerable extension of the periodic table; citation_author=GT Seaborg; citation_volume=46; citation_issue=10; citation_publication_date=1969; citation_pages=626-634; citation_doi=10.1021/ed046p626; citation_id=CR82"/> <meta name="citation_reference" content="citation_journal_title=Chem. Rev.; citation_title=Molecular hexafluorides; citation_author=K Seppelt; citation_volume=115; citation_issue=2; citation_publication_date=2015; citation_pages=1296-1306; citation_doi=10.1021/cr5001783; citation_id=CR83"/> <meta name="citation_reference" content="citation_journal_title=Found. Chem.; citation_title=Charles Janet: unrecognized genius of the periodic system; citation_author=PJ Stewart; citation_volume=12; citation_issue=1; citation_publication_date=2010; citation_pages=5-15; citation_doi=10.1007/s10698-008-9062-5; citation_id=CR84"/> <meta name="citation_reference" content="citation_title=Noble-gas compounds; citation_inbook_title=Kirk-Othmer Encyclopedia of Chemical Technology; citation_publication_date=2003; citation_id=CR85; citation_author=GJ Schrobilgen; citation_author=MD Moran; citation_publisher=Wiley"/> <meta name="citation_reference" content="citation_journal_title=Angew. Chem. Int. Ed.; citation_title=100th anniversary of Bohr’s model of the atom; citation_author=WHE Schwarz; citation_volume=52; citation_issue=47; citation_publication_date=2013; citation_pages=12228-12238; citation_doi=10.1002/anie.201306024; citation_id=CR86"/> <meta name="citation_reference" content="citation_journal_title=Science; citation_title=Xenon as a complex ligand: the tetraxenono gold(II) cation in AuXe4 2+(Sb2F11 −)2 ; citation_author=K Seppelt, S Seidel; citation_volume=290; citation_issue=5489; citation_publication_date=2000; citation_pages=117-118; citation_doi=10.1126/science.290.5489.117; citation_id=CR87"/> <meta name="citation_reference" content="Schwarz, W. H. E. (2016) Letter to the author (July 2016)"/> <meta name="citation_reference" content="citation_title=A Physicist’s Chart of the Chemical Elements; citation_publication_date=1989; citation_id=CR89; citation_author=T Stowe; citation_publisher=Instruments Research and Industry Inc."/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. A; citation_title=Noble gas monoxides stabilized in dipolar cavity: a theoretical study; citation_author=P Szarek, W Grochala; citation_volume=119; citation_issue=11; citation_publication_date=2015; citation_pages=2483-2489; citation_doi=10.1021/jp508786y; citation_id=CR90"/> <meta name="citation_reference" content="citation_journal_title=Chem. Phys. Lett.; citation_title=Theoretical prediction of the lifetime of the metastable helium compound: HHeF; citation_author=T Takayanagi, A Wada; citation_volume=352; citation_issue=1–2; citation_publication_date=2002; citation_pages=91-98; citation_doi=10.1016/S0009-2614(01)01436-1; citation_id=CR201"/> <meta name="citation_reference" content="Tarantola, A.: A Periodic Table of the elements, based on the electronic structure of the atoms. (2000) chemistry/0009002"/> <meta name="citation_reference" content="Tarantola, A.: The Periodic Table of the elements and the ionization potentials. (2002) physchem/0201017"/> <meta name="citation_reference" content="citation_journal_title=J. Am. Chem. Soc.; citation_title=Noble-gas complexes with BeO—infrared-spectra of NG-BeO (NG = Ar, Kr, Xe); citation_author=CA Thompson, L Andrews; citation_volume=116; citation_issue=1; citation_publication_date=1994; citation_pages=423-424; citation_doi=10.1021/ja00080a069; citation_id=CR93"/> <meta name="citation_reference" content="citation_journal_title=Nature; citation_title=A high-pressure van der Waals compound in solid nitrogen–helium mixtures; citation_author=WL Vos, LW Finger, RJ Hemley, JZ Hu, HK Mao, JA Schouten; citation_volume=358; citation_publication_date=1992; citation_pages=46-48; citation_doi=10.1038/358046a0; citation_id=CR94"/> <meta name="citation_reference" content="citation_journal_title=Angew. Chem. Int. Ed.; citation_title=Icon of chemistry: the periodic system of chemical elements in the new century; citation_author=S-G Wang, WHE Schwarz; citation_volume=48; citation_issue=19; citation_publication_date=2009; citation_pages=2-14; citation_doi=10.1002/anie.200800827; citation_id=CR95"/> <meta name="citation_reference" content="citation_journal_title=Chem. Eur. J.; citation_title=Matrix infrared spectroscopy and quantum-chemical calculations for the coinage-metal fluorides: comparisons of Ar–AuF, Ne–AuF, and molecules MF2 and MF3 ; citation_author=X Wang, L Andrews, F Brosi, S Riedel; citation_volume=19; citation_issue=4; citation_publication_date=2013; citation_pages=1397-1409; citation_doi=10.1002/chem.201203306; citation_id=CR96"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. A; citation_title=Infrared spectra of NgBeS (Ng = Ne, Ar, Kr, Xe) and BeS2 in noble-gas matrices; citation_author=Q Wang, X Wang; citation_volume=117; citation_issue=7; citation_publication_date=2013; citation_pages=1508-1513; citation_doi=10.1021/jp311901a; citation_id=CR97"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. A; citation_title=Ab initio structures and stabilities of doubly charged diatomic metal helides for the first row transition metals; citation_author=DJD Wilson, CJ Marsden, EI Nagy-Felsobuki; citation_volume=106; citation_issue=32; citation_publication_date=2002; citation_pages=7348-7354; citation_doi=10.1021/jp0203503; citation_id=CR98"/> <meta name="citation_reference" content="citation_journal_title=J. Am. Chem. Soc.; citation_title=Prediction of a metastable helium compound: HHeF; citation_author=MW Wong; citation_volume=122; citation_issue=26; citation_publication_date=2000; citation_pages=6289-6290; citation_doi=10.1021/ja9938175; citation_id=CR99"/> <meta name="citation_reference" content="citation_journal_title=Nat. Chem.; citation_title=Stability of xenon oxides at high pressures; citation_author=Q Zhu, DY Jung, AR Oganov, CW Glass, C Gatti, AO Lyakhov; citation_volume=5; citation_issue=1; citation_publication_date=2013; citation_pages=61-65; citation_doi=10.1038/nchem.1497; citation_id=CR100"/> <meta name="citation_reference" content="citation_journal_title=Nat. Chem.; citation_title=Reactions of xenon with iron and nickel are predicted in the Earth’s inner core; citation_author=L Zhu, H Liu, CJ Pickard, G Zou, Y Ma; citation_volume=6; citation_issue=7; citation_publication_date=2014; citation_pages=644-648; citation_doi=10.1038/nchem.1925; citation_id=CR101"/> <meta name="citation_reference" content="citation_journal_title=Chem. Phys. Lett.; citation_title=Theoretical study of RgMF (Rg = He, Ne; M = Cu, Ag, Au): bonded structures of helium; citation_author=L Zou, Y Liu, JE Boggs; citation_volume=482; citation_issue=4–6; citation_publication_date=2009; citation_pages=207-210; citation_doi=10.1016/j.cplett.2009.10.010; citation_id=CR102"/> <meta name="citation_reference" content="citation_journal_title=J. Phys. Chem. A; citation_title=On the covalent character of rare gas bonding interactions: a new kind of weak interaction; citation_author=W Zou, D Nori-Shargh, JE Boggs; citation_volume=117; citation_issue=1; citation_publication_date=2013; citation_pages=207-212; citation_doi=10.1021/jp3104535; citation_id=CR103"/> <meta name="citation_author" content="Grochala, Wojciech"/> <meta name="citation_author_email" content="w.grochala@cent.uw.edu.pl"/> <meta name="citation_author_institution" content="Center of New Technologies, University of Warsaw, Warsaw, Poland"/> <meta name="format-detection" content="telephone=no"/> <meta name="citation_cover_date" content="2018/10/01"/> <meta property="og:url" content="https://link.springer.com/article/10.1007/s10698-017-9302-7"/> <meta property="og:type" content="article"/> <meta property="og:site_name" content="SpringerLink"/> <meta property="og:title" content="On the position of helium and neon in the Periodic Table of Elements - Foundations of Chemistry"/> <meta property="og:description" content="Helium and neon, the two lightest noble gases, have been traditionally positioned by IUPAC in the Group 18 of the Periodic Table of Elements, together with argon, and other unreactive or moderately reactive gaseous elements (krypton, xenon, radon), and oganesson. In this account we revive the old discussion on the possible placement of helium in the Group 2, while preserving the position of neon in Group 18. We provide quantum-chemical arguments for such scenario—as well as other qualitative and quantitative arguments—and we describe previous suggestions in the literature which support it or put it into question. To this author’s own taste, He should be placed in Group 2."/> <meta property="og:image" content="https://static-content.springer.com/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig1_HTML.gif"/> <meta name="format-detection" content="telephone=no"> <link rel="apple-touch-icon" sizes="180x180" href=/oscar-static/img/favicons/darwin/apple-touch-icon-92e819bf8a.png> <link rel="icon" type="image/png" sizes="192x192" href=/oscar-static/img/favicons/darwin/android-chrome-192x192-6f081ca7e5.png> <link rel="icon" type="image/png" sizes="32x32" href=/oscar-static/img/favicons/darwin/favicon-32x32-1435da3e82.png> <link rel="icon" type="image/png" sizes="16x16" href=/oscar-static/img/favicons/darwin/favicon-16x16-ed57f42bd2.png> <link rel="shortcut icon" data-test="shortcut-icon" href=/oscar-static/img/favicons/darwin/favicon-c6d59aafac.ico> <meta name="theme-color" content="#e6e6e6">   <link rel="stylesheet" media="print" href=/oscar-static/app-springerlink/css/print-b8af42253b.css> <style> html{text-size-adjust:100%;line-height:1.15}body{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;line-height:1.8;margin:0}details,main{display:block}h1{font-size:2em;margin:.67em 0}a{background-color:transparent;color:#025e8d}sub{bottom:-.25em;font-size:75%;line-height:0;position:relative;vertical-align:baseline}img{border:0;height:auto;max-width:100%;vertical-align:middle}button,input{font-family:inherit;font-size:100%;line-height:1.15;margin:0;overflow:visible}button{text-transform:none}[type=button],[type=submit],button{-webkit-appearance:button}[type=search]{-webkit-appearance:textfield;outline-offset:-2px}summary{display:list-item}[hidden]{display:none}button{cursor:pointer}svg{height:1rem;width:1rem} </style> <style>@media only print, only all and (prefers-color-scheme: no-preference), only all and (prefers-color-scheme: light), only all and (prefers-color-scheme: dark) { body{background:#fff;color:#222;font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;line-height:1.8;min-height:100%}a{color:#025e8d;text-decoration:underline;text-decoration-skip-ink:auto}button{cursor:pointer}img{border:0;height:auto;max-width:100%;vertical-align:middle}html{box-sizing:border-box;font-size:100%;height:100%;overflow-y:scroll}h1{font-size:2.25rem}h2{font-size:1.75rem}h1,h2,h4{font-weight:700;line-height:1.2}h4{font-size:1.25rem}body{font-size:1.125rem}*{box-sizing:inherit}p{margin-bottom:2rem;margin-top:0}p:last-of-type{margin-bottom:0}.c-ad{text-align:center}@media only screen and (min-width:480px){.c-ad{padding:8px}}.c-ad--728x90{display:none}.c-ad--728x90 .c-ad__inner{min-height:calc(1.5em + 94px)}@media only screen and (min-width:876px){.js .c-ad--728x90{display:none}}.c-ad__label{color:#333;font-size:.875rem;font-weight:400;line-height:1.5;margin-bottom:4px}.c-ad__label,.c-status-message{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif}.c-status-message{align-items:center;box-sizing:border-box;display:flex;position:relative;width:100%}.c-status-message :last-child{margin-bottom:0}.c-status-message--boxed{background-color:#fff;border:1px solid #ccc;line-height:1.4;padding:16px}.c-status-message__heading{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;font-size:.875rem;font-weight:700}.c-status-message__icon{fill:currentcolor;display:inline-block;flex:0 0 auto;height:1.5em;margin-right:8px;transform:translate(0);vertical-align:text-top;width:1.5em}.c-status-message__icon--top{align-self:flex-start}.c-status-message--info .c-status-message__icon{color:#003f8d}.c-status-message--boxed.c-status-message--info{border-bottom:4px solid #003f8d}.c-status-message--error .c-status-message__icon{color:#c40606}.c-status-message--boxed.c-status-message--error{border-bottom:4px solid #c40606}.c-status-message--success .c-status-message__icon{color:#00b8b0}.c-status-message--boxed.c-status-message--success{border-bottom:4px solid #00b8b0}.c-status-message--warning .c-status-message__icon{color:#edbc53}.c-status-message--boxed.c-status-message--warning{border-bottom:4px solid #edbc53}.eds-c-header{background-color:#fff;border-bottom:2px solid #01324b;font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;font-size:1rem;line-height:1.5;padding:8px 0 0}.eds-c-header__container{align-items:center;display:flex;flex-wrap:nowrap;gap:8px 16px;justify-content:space-between;margin:0 auto 8px;max-width:1280px;padding:0 8px;position:relative}.eds-c-header__nav{border-top:2px solid #c5e0f4;padding-top:4px;position:relative}.eds-c-header__nav-container{align-items:center;display:flex;flex-wrap:wrap;margin:0 auto 4px;max-width:1280px;padding:0 8px;position:relative}.eds-c-header__nav-container>:not(:last-child){margin-right:32px}.eds-c-header__link-container{align-items:center;display:flex;flex:1 0 auto;gap:8px 16px;justify-content:space-between}.eds-c-header__list{list-style:none;margin:0;padding:0}.eds-c-header__list-item{font-weight:700;margin:0 auto;max-width:1280px;padding:8px}.eds-c-header__list-item:not(:last-child){border-bottom:2px solid #c5e0f4}.eds-c-header__item{color:inherit}@media only screen and (min-width:768px){.eds-c-header__item--menu{display:none;visibility:hidden}.eds-c-header__item--menu:first-child+*{margin-block-start:0}}.eds-c-header__item--inline-links{display:none;visibility:hidden}@media only screen and (min-width:768px){.eds-c-header__item--inline-links{display:flex;gap:16px 16px;visibility:visible}}.eds-c-header__item--divider:before{border-left:2px solid #c5e0f4;content:"";height:calc(100% - 16px);margin-left:-15px;position:absolute;top:8px}.eds-c-header__brand{padding:16px 8px}.eds-c-header__brand a{display:block;line-height:1;text-decoration:none}.eds-c-header__brand img{height:1.5rem;width:auto}.eds-c-header__link{color:inherit;display:inline-block;font-weight:700;padding:16px 8px;position:relative;text-decoration-color:transparent;white-space:nowrap;word-break:normal}.eds-c-header__icon{fill:currentcolor;display:inline-block;font-size:1.5rem;height:1em;transform:translate(0);vertical-align:bottom;width:1em}.eds-c-header__icon+*{margin-left:8px}.eds-c-header__expander{background-color:#f0f7fc}.eds-c-header__search{display:block;padding:24px 0}@media only screen and (min-width:768px){.eds-c-header__search{max-width:70%}}.eds-c-header__search-container{position:relative}.eds-c-header__search-label{color:inherit;display:inline-block;font-weight:700;margin-bottom:8px}.eds-c-header__search-input{background-color:#fff;border:1px solid #000;padding:8px 48px 8px 8px;width:100%}.eds-c-header__search-button{background-color:transparent;border:0;color:inherit;height:100%;padding:0 8px;position:absolute;right:0}.has-tethered.eds-c-header__expander{border-bottom:2px solid #01324b;left:0;margin-top:-2px;top:100%;width:100%;z-index:10}@media only screen and (min-width:768px){.has-tethered.eds-c-header__expander--menu{display:none;visibility:hidden}}.has-tethered .eds-c-header__heading{display:none;visibility:hidden}.has-tethered .eds-c-header__heading:first-child+*{margin-block-start:0}.has-tethered .eds-c-header__search{margin:auto}.eds-c-header__heading{margin:0 auto;max-width:1280px;padding:16px 16px 0}.eds-c-pagination{align-items:center;display:flex;flex-wrap:wrap;font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;font-size:.875rem;gap:16px 0;justify-content:center;line-height:1.4;list-style:none;margin:0;padding:32px 0}@media only screen and (min-width:480px){.eds-c-pagination{padding:32px 16px}}.eds-c-pagination__item{margin-right:8px}.eds-c-pagination__item--prev{margin-right:16px}.eds-c-pagination__item--next .eds-c-pagination__link,.eds-c-pagination__item--prev .eds-c-pagination__link{padding:16px 8px}.eds-c-pagination__item--next{margin-left:8px}.eds-c-pagination__item:last-child{margin-right:0}.eds-c-pagination__link{align-items:center;color:#222;cursor:pointer;display:inline-block;font-size:1rem;margin:0;padding:16px 24px;position:relative;text-align:center;transition:all .2s ease 0s}.eds-c-pagination__link:visited{color:#222}.eds-c-pagination__link--disabled{border-color:#555;color:#555;cursor:default}.eds-c-pagination__link--active{background-color:#01324b;background-image:none;border-radius:8px;color:#fff}.eds-c-pagination__link--active:focus,.eds-c-pagination__link--active:hover,.eds-c-pagination__link--active:visited{color:#fff}.eds-c-pagination__link-container{align-items:center;display:flex}.eds-c-pagination__icon{fill:#222;height:1.5rem;width:1.5rem}.eds-c-pagination__icon--disabled{fill:#555}.eds-c-pagination__visually-hidden{clip:rect(0,0,0,0);border:0;clip-path:inset(50%);height:1px;overflow:hidden;padding:0;position:absolute!important;white-space:nowrap;width:1px}.c-breadcrumbs{color:#333;font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;font-size:1rem;list-style:none;margin:0;padding:0}.c-breadcrumbs>li{display:inline}svg.c-breadcrumbs__chevron{fill:#333;height:10px;margin:0 .25rem;width:10px}.c-breadcrumbs--contrast,.c-breadcrumbs--contrast .c-breadcrumbs__link{color:#fff}.c-breadcrumbs--contrast svg.c-breadcrumbs__chevron{fill:#fff}@media only screen and (max-width:479px){.c-breadcrumbs .c-breadcrumbs__item{display:none}.c-breadcrumbs .c-breadcrumbs__item:last-child,.c-breadcrumbs .c-breadcrumbs__item:nth-last-child(2){display:inline}}.c-skip-link{background:#01324b;bottom:auto;color:#fff;font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;font-size:1rem;padding:8px;position:absolute;text-align:center;transform:translateY(-100%);width:100%;z-index:9999}@media (prefers-reduced-motion:reduce){.c-skip-link{transition:top .3s ease-in-out 0s}}@media print{.c-skip-link{display:none}}.c-skip-link:active,.c-skip-link:hover,.c-skip-link:link,.c-skip-link:visited{color:#fff}.c-skip-link:focus{transform:translateY(0)}.l-with-sidebar{display:flex;flex-wrap:wrap}.l-with-sidebar>*{margin:0}.l-with-sidebar__sidebar{flex-basis:var(--with-sidebar--basis,400px);flex-grow:1}.l-with-sidebar>:not(.l-with-sidebar__sidebar){flex-basis:0px;flex-grow:999;min-width:var(--with-sidebar--min,53%)}.l-with-sidebar>:first-child{padding-right:4rem}@supports (gap:1em){.l-with-sidebar>:first-child{padding-right:0}.l-with-sidebar{gap:var(--with-sidebar--gap,4rem)}}.c-header__link{color:inherit;display:inline-block;font-weight:700;padding:16px 8px;position:relative;text-decoration-color:transparent;white-space:nowrap;word-break:normal}.app-masthead__colour-4{--background-color:#ff9500;--gradient-light:rgba(0,0,0,.5);--gradient-dark:rgba(0,0,0,.8)}.app-masthead{background:var(--background-color,#0070a8);position:relative}.app-masthead:after{background:radial-gradient(circle at top right,var(--gradient-light,rgba(0,0,0,.4)),var(--gradient-dark,rgba(0,0,0,.7)));bottom:0;content:"";left:0;position:absolute;right:0;top:0}@media only screen and (max-width:479px){.app-masthead:after{background:linear-gradient(225deg,var(--gradient-light,rgba(0,0,0,.4)),var(--gradient-dark,rgba(0,0,0,.7)))}}.app-masthead__container{color:var(--masthead-color,#fff);margin:0 auto;max-width:1280px;padding:0 16px;position:relative;z-index:1}.u-button{align-items:center;background-color:#01324b;background-image:none;border:4px solid transparent;border-radius:32px;cursor:pointer;display:inline-flex;font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;font-size:.875rem;font-weight:700;justify-content:center;line-height:1.3;margin:0;padding:16px 32px;position:relative;transition:all .2s ease 0s;width:auto}.u-button svg,.u-button--contrast svg,.u-button--primary svg,.u-button--secondary svg,.u-button--tertiary svg{fill:currentcolor}.u-button,.u-button:visited{color:#fff}.u-button,.u-button:hover{box-shadow:0 0 0 1px #01324b;text-decoration:none}.u-button:hover{border:4px solid #fff}.u-button:focus{border:4px solid #fc0;box-shadow:none;outline:0;text-decoration:none}.u-button:focus,.u-button:hover{background-color:#fff;background-image:none;color:#01324b}.app-masthead--pastel .c-pdf-download .u-button--primary:focus svg path,.app-masthead--pastel .c-pdf-download .u-button--primary:hover svg path,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--primary:focus svg path,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--primary:hover svg path,.u-button--primary:focus svg path,.u-button--primary:hover svg path,.u-button:focus svg path,.u-button:hover svg path{fill:#01324b}.u-button--primary{background-color:#01324b;background-image:none;border:4px solid transparent;box-shadow:0 0 0 1px #01324b;color:#fff;font-weight:700}.u-button--primary:visited{color:#fff}.u-button--primary:hover{border:4px solid #fff;box-shadow:0 0 0 1px #01324b;text-decoration:none}.u-button--primary:focus{border:4px solid #fc0;box-shadow:none;outline:0;text-decoration:none}.u-button--primary:focus,.u-button--primary:hover{background-color:#fff;background-image:none;color:#01324b}.u-button--secondary{background-color:#fff;border:4px solid #fff;color:#01324b;font-weight:700}.u-button--secondary:visited{color:#01324b}.u-button--secondary:hover{border:4px solid #01324b;box-shadow:none}.u-button--secondary:focus,.u-button--secondary:hover{background-color:#01324b;color:#fff}.app-masthead--pastel .c-pdf-download .u-button--secondary:focus svg path,.app-masthead--pastel .c-pdf-download .u-button--secondary:hover svg path,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--secondary:focus svg path,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--secondary:hover svg path,.u-button--secondary:focus svg path,.u-button--secondary:hover svg path,.u-button--tertiary:focus svg path,.u-button--tertiary:hover svg path{fill:#fff}.u-button--tertiary{background-color:#ebf1f5;border:4px solid transparent;box-shadow:none;color:#666;font-weight:700}.u-button--tertiary:visited{color:#666}.u-button--tertiary:hover{border:4px solid #01324b;box-shadow:none}.u-button--tertiary:focus,.u-button--tertiary:hover{background-color:#01324b;color:#fff}.u-button--contrast{background-color:transparent;background-image:none;color:#fff;font-weight:400}.u-button--contrast:visited{color:#fff}.u-button--contrast,.u-button--contrast:focus,.u-button--contrast:hover{border:4px solid #fff}.u-button--contrast:focus,.u-button--contrast:hover{background-color:#fff;background-image:none;color:#000}.u-button--contrast:focus svg path,.u-button--contrast:hover svg path{fill:#000}.u-button--disabled,.u-button:disabled{background-color:transparent;background-image:none;border:4px solid #ccc;color:#000;cursor:default;font-weight:400;opacity:.7}.u-button--disabled svg,.u-button:disabled svg{fill:currentcolor}.u-button--disabled:visited,.u-button:disabled:visited{color:#000}.u-button--disabled:focus,.u-button--disabled:hover,.u-button:disabled:focus,.u-button:disabled:hover{border:4px solid #ccc;text-decoration:none}.u-button--disabled:focus,.u-button--disabled:hover,.u-button:disabled:focus,.u-button:disabled:hover{background-color:transparent;background-image:none;color:#000}.u-button--disabled:focus svg path,.u-button--disabled:hover svg path,.u-button:disabled:focus svg path,.u-button:disabled:hover svg path{fill:#000}.u-button--small,.u-button--xsmall{font-size:.875rem;padding:2px 8px}.u-button--small{padding:8px 16px}.u-button--large{font-size:1.125rem;padding:10px 35px}.u-button--full-width{display:flex;width:100%}.u-button--icon-left svg{margin-right:8px}.u-button--icon-right svg{margin-left:8px}.u-clear-both{clear:both}.u-container{margin:0 auto;max-width:1280px;padding:0 16px}.u-justify-content-space-between{justify-content:space-between}.u-display-none{display:none}.js .u-js-hide,.u-hide{display:none;visibility:hidden}.u-visually-hidden{clip:rect(0,0,0,0);border:0;clip-path:inset(50%);height:1px;overflow:hidden;padding:0;position:absolute!important;white-space:nowrap;width:1px}.u-icon{fill:currentcolor;display:inline-block;height:1em;transform:translate(0);vertical-align:text-top;width:1em}.u-list-reset{list-style:none;margin:0;padding:0}.u-ma-16{margin:16px}.u-mt-0{margin-top:0}.u-mt-24{margin-top:24px}.u-mt-32{margin-top:32px}.u-mb-8{margin-bottom:8px}.u-mb-32{margin-bottom:32px}.u-button-reset{background-color:transparent;border:0;padding:0}.u-sans-serif{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif}.u-serif{font-family:Merriweather,serif}h1,h2,h4{-webkit-font-smoothing:antialiased}p{overflow-wrap:break-word;word-break:break-word}.u-h4{font-size:1.25rem;font-weight:700;line-height:1.2}.u-mbs-0{margin-block-start:0!important}.c-article-header{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif}.c-article-identifiers{color:#6f6f6f;display:flex;flex-wrap:wrap;font-size:1rem;line-height:1.3;list-style:none;margin:0 0 8px;padding:0}.c-article-identifiers__item{border-right:1px solid #6f6f6f;list-style:none;margin-right:8px;padding-right:8px}.c-article-identifiers__item:last-child{border-right:0;margin-right:0;padding-right:0}@media only screen and (min-width:876px){.c-article-title{font-size:1.875rem;line-height:1.2}}.c-article-author-list{display:inline;font-size:1rem;list-style:none;margin:0 8px 0 0;padding:0;width:100%}.c-article-author-list__item{display:inline;padding-right:0}.c-article-author-list__show-more{display:none;margin-right:4px}.c-article-author-list__button,.js .c-article-author-list__item--hide,.js .c-article-author-list__show-more{display:none}.js .c-article-author-list--long .c-article-author-list__show-more,.js .c-article-author-list--long+.c-article-author-list__button{display:inline}@media only screen and (max-width:767px){.js .c-article-author-list__item--hide-small-screen{display:none}.js .c-article-author-list--short .c-article-author-list__show-more,.js .c-article-author-list--short+.c-article-author-list__button{display:inline}}#uptodate-client,.js .c-article-author-list--expanded .c-article-author-list__show-more{display:none!important}.js .c-article-author-list--expanded .c-article-author-list__item--hide-small-screen{display:inline!important}.c-article-author-list__button,.c-button-author-list{background:#ebf1f5;border:4px solid #ebf1f5;border-radius:20px;color:#666;font-size:.875rem;line-height:1.4;padding:2px 11px 2px 8px;text-decoration:none}.c-article-author-list__button svg,.c-button-author-list svg{margin:1px 4px 0 0}.c-article-author-list__button:hover,.c-button-author-list:hover{background:#025e8d;border-color:transparent;color:#fff}.c-article-body .c-article-access-provider{padding:8px 16px}.c-article-body .c-article-access-provider,.c-notes{border:1px solid #d5d5d5;border-image:initial;border-left:none;border-right:none;margin:24px 0}.c-article-body .c-article-access-provider__text{color:#555}.c-article-body .c-article-access-provider__text,.c-notes__text{font-size:1rem;margin-bottom:0;padding-bottom:2px;padding-top:2px;text-align:center}.c-article-body .c-article-author-affiliation__address{color:inherit;font-weight:700;margin:0}.c-article-body .c-article-author-affiliation__authors-list{list-style:none;margin:0;padding:0}.c-article-body .c-article-author-affiliation__authors-item{display:inline;margin-left:0}.c-article-authors-search{margin-bottom:24px;margin-top:0}.c-article-authors-search__item,.c-article-authors-search__title{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif}.c-article-authors-search__title{color:#626262;font-size:1.05rem;font-weight:700;margin:0;padding:0}.c-article-authors-search__item{font-size:1rem}.c-article-authors-search__text{margin:0}.c-code-block{border:1px solid #fff;font-family:monospace;margin:0 0 24px;padding:20px}.c-code-block__heading{font-weight:400;margin-bottom:16px}.c-code-block__line{display:block;overflow-wrap:break-word;white-space:pre-wrap}.c-article-share-box{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;margin-bottom:24px}.c-article-share-box__description{font-size:1rem;margin-bottom:8px}.c-article-share-box__no-sharelink-info{font-size:.813rem;font-weight:700;margin-bottom:24px;padding-top:4px}.c-article-share-box__only-read-input{border:1px solid #d5d5d5;box-sizing:content-box;display:inline-block;font-size:.875rem;font-weight:700;height:24px;margin-bottom:8px;padding:8px 10px}.c-article-share-box__additional-info{color:#626262;font-size:.813rem}.c-article-share-box__button{background:#fff;box-sizing:content-box;text-align:center}.c-article-share-box__button--link-like{background-color:transparent;border:0;color:#025e8d;cursor:pointer;font-size:.875rem;margin-bottom:8px;margin-left:10px}.c-article-associated-content__container .c-article-associated-content__collection-label{font-size:.875rem;line-height:1.4}.c-article-associated-content__container .c-article-associated-content__collection-title{line-height:1.3}.c-reading-companion{clear:both;min-height:389px}.c-reading-companion__figures-list,.c-reading-companion__references-list{list-style:none;min-height:389px;padding:0}.c-reading-companion__references-list--numeric{list-style:decimal inside}.c-reading-companion__figure-item{border-top:1px solid #d5d5d5;font-size:1rem;padding:16px 8px 16px 0}.c-reading-companion__figure-item:first-child{border-top:none;padding-top:8px}.c-reading-companion__reference-item{font-size:1rem}.c-reading-companion__reference-item:first-child{border-top:none}.c-reading-companion__reference-item a{word-break:break-word}.c-reading-companion__reference-citation{display:inline}.c-reading-companion__reference-links{font-size:.813rem;font-weight:700;list-style:none;margin:8px 0 0;padding:0;text-align:right}.c-reading-companion__reference-links>a{display:inline-block;padding-left:8px}.c-reading-companion__reference-links>a:first-child{display:inline-block;padding-left:0}.c-reading-companion__figure-title{display:block;font-size:1.25rem;font-weight:700;line-height:1.2;margin:0 0 8px}.c-reading-companion__figure-links{display:flex;justify-content:space-between;margin:8px 0 0}.c-reading-companion__figure-links>a{align-items:center;display:flex}.c-article-section__figure-caption{display:block;margin-bottom:8px;word-break:break-word}.c-article-section__figure .video,p.app-article-masthead__access--above-download{margin:0 0 16px}.c-article-section__figure-description{font-size:1rem}.c-article-section__figure-description>*{margin-bottom:0}.c-cod{display:block;font-size:1rem;width:100%}.c-cod__form{background:#ebf0f3}.c-cod__prompt{font-size:1.125rem;line-height:1.3;margin:0 0 24px}.c-cod__label{display:block;margin:0 0 4px}.c-cod__row{display:flex;margin:0 0 16px}.c-cod__row:last-child{margin:0}.c-cod__input{border:1px solid #d5d5d5;border-radius:2px;flex-shrink:0;margin:0;padding:13px}.c-cod__input--submit{background-color:#025e8d;border:1px solid #025e8d;color:#fff;flex-shrink:1;margin-left:8px;transition:background-color .2s ease-out 0s,color .2s ease-out 0s}.c-cod__input--submit-single{flex-basis:100%;flex-shrink:0;margin:0}.c-cod__input--submit:focus,.c-cod__input--submit:hover{background-color:#fff;color:#025e8d}.save-data .c-article-author-institutional-author__sub-division,.save-data .c-article-equation__number,.save-data .c-article-figure-description,.save-data .c-article-fullwidth-content,.save-data .c-article-main-column,.save-data .c-article-satellite-article-link,.save-data .c-article-satellite-subtitle,.save-data .c-article-table-container,.save-data .c-blockquote__body,.save-data .c-code-block__heading,.save-data .c-reading-companion__figure-title,.save-data .c-reading-companion__reference-citation,.save-data .c-site-messages--nature-briefing-email-variant .serif,.save-data .c-site-messages--nature-briefing-email-variant.serif,.save-data .serif,.save-data .u-serif,.save-data h1,.save-data h2,.save-data h3{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif}.c-pdf-download__link{display:flex;flex:1 1 0%;padding:13px 24px}.c-pdf-download__link:hover{text-decoration:none}@media only screen and (min-width:768px){.c-context-bar--sticky .c-pdf-download__link{align-items:center;flex:1 1 183px}}@media only screen and (max-width:320px){.c-context-bar--sticky .c-pdf-download__link{padding:16px}}.c-article-body .c-article-recommendations-list,.c-book-body .c-article-recommendations-list{display:flex;flex-direction:row;gap:16px 16px;margin:0;max-width:100%;padding:16px 0 0}.c-article-body .c-article-recommendations-list__item,.c-book-body .c-article-recommendations-list__item{flex:1 1 0%}@media only screen and (max-width:767px){.c-article-body .c-article-recommendations-list,.c-book-body .c-article-recommendations-list{flex-direction:column}}.c-article-body .c-article-recommendations-card__authors{display:none;font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;font-size:.875rem;line-height:1.5;margin:0 0 8px}@media only screen and (max-width:767px){.c-article-body .c-article-recommendations-card__authors{display:block;margin:0}}.c-article-body .c-article-history{margin-top:24px}.app-article-metrics-bar p{margin:0}.app-article-masthead{display:flex;flex-direction:column;gap:16px 16px;padding:16px 0 24px}.app-article-masthead__info{display:flex;flex-direction:column;flex-grow:1}.app-article-masthead__brand{border-top:1px solid hsla(0,0%,100%,.8);display:flex;flex-direction:column;flex-shrink:0;gap:8px 8px;min-height:96px;padding:16px 0 0}.app-article-masthead__brand img{border:1px solid #fff;border-radius:8px;box-shadow:0 4px 15px 0 hsla(0,0%,50%,.25);height:auto;left:0;position:absolute;width:72px}.app-article-masthead__journal-link{display:block;font-size:1.125rem;font-weight:700;margin:0 0 8px;max-width:400px;padding:0 0 0 88px;position:relative}.app-article-masthead__journal-title{-webkit-box-orient:vertical;-webkit-line-clamp:3;display:-webkit-box;overflow:hidden}.app-article-masthead__submission-link{align-items:center;display:flex;font-size:1rem;gap:4px 4px;margin:0 0 0 88px}.app-article-masthead__access{align-items:center;display:flex;flex-wrap:wrap;font-size:.875rem;font-weight:300;gap:4px 4px;margin:0}.app-article-masthead__buttons{display:flex;flex-flow:column wrap;gap:16px 16px}.app-article-masthead__access svg,.app-masthead--pastel .c-pdf-download .u-button--primary svg,.app-masthead--pastel .c-pdf-download .u-button--secondary svg,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--primary svg,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--secondary svg{fill:currentcolor}.app-article-masthead a{color:#fff}.app-masthead--pastel .c-pdf-download .u-button--primary,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--primary{background-color:#025e8d;background-image:none;border:2px solid transparent;box-shadow:none;color:#fff;font-weight:700}.app-masthead--pastel .c-pdf-download .u-button--primary:visited,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--primary:visited{color:#fff}.app-masthead--pastel .c-pdf-download .u-button--primary:hover,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--primary:hover{text-decoration:none}.app-masthead--pastel .c-pdf-download .u-button--primary:focus,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--primary:focus{border:4px solid #fc0;box-shadow:none;outline:0;text-decoration:none}.app-masthead--pastel .c-pdf-download .u-button--primary:focus,.app-masthead--pastel .c-pdf-download .u-button--primary:hover,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--primary:focus,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--primary:hover{background-color:#fff;background-image:none;color:#01324b}.app-masthead--pastel .c-pdf-download .u-button--primary:hover,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--primary:hover{background:0 0;border:2px solid #025e8d;box-shadow:none;color:#025e8d}.app-masthead--pastel .c-pdf-download .u-button--secondary,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--secondary{background:0 0;border:2px solid #025e8d;color:#025e8d;font-weight:700}.app-masthead--pastel .c-pdf-download .u-button--secondary:visited,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--secondary:visited{color:#01324b}.app-masthead--pastel .c-pdf-download .u-button--secondary:hover,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--secondary:hover{background-color:#01324b;background-color:#025e8d;border:2px solid transparent;box-shadow:none;color:#fff}.app-masthead--pastel .c-pdf-download .u-button--secondary:focus,.c-context-bar--sticky .c-context-bar__container .c-pdf-download .u-button--secondary:focus{background-color:#fff;background-image:none;border:4px solid #fc0;color:#01324b}@media only screen and (min-width:768px){.app-article-masthead{flex-direction:row;gap:64px 64px;padding:24px 0}.app-article-masthead__brand{border:0;padding:0}.app-article-masthead__brand img{height:auto;position:static;width:auto}.app-article-masthead__buttons{align-items:center;flex-direction:row;margin-top:auto}.app-article-masthead__journal-link{display:flex;flex-direction:column;gap:24px 24px;margin:0 0 8px;padding:0}.app-article-masthead__submission-link{margin:0}}@media only screen and (min-width:1024px){.app-article-masthead__brand{flex-basis:400px}}.app-article-masthead .c-article-identifiers{font-size:.875rem;font-weight:300;line-height:1;margin:0 0 8px;overflow:hidden;padding:0}.app-article-masthead .c-article-identifiers--cite-list{margin:0 0 16px}.app-article-masthead .c-article-identifiers *{color:#fff}.app-article-masthead .c-cod{display:none}.app-article-masthead .c-article-identifiers__item{border-left:1px solid #fff;border-right:0;margin:0 17px 8px -9px;padding:0 0 0 8px}.app-article-masthead .c-article-identifiers__item--cite{border-left:0}.app-article-metrics-bar{display:flex;flex-wrap:wrap;font-size:1rem;padding:16px 0 0;row-gap:24px}.app-article-metrics-bar__item{padding:0 16px 0 0}.app-article-metrics-bar__count{font-weight:700}.app-article-metrics-bar__label{font-weight:400;padding-left:4px}.app-article-metrics-bar__icon{height:auto;margin-right:4px;margin-top:-4px;width:auto}.app-article-metrics-bar__arrow-icon{margin:4px 0 0 4px}.app-article-metrics-bar a{color:#000}.app-article-metrics-bar .app-article-metrics-bar__item--metrics{padding-right:0}.app-overview-section .c-article-author-list,.app-overview-section__authors{line-height:2}.app-article-metrics-bar{margin-top:8px}.c-book-toc-pagination+.c-book-section__back-to-top{margin-top:0}.c-article-body .c-article-access-provider__text--chapter{color:#222;font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;padding:20px 0}.c-article-body .c-article-access-provider__text--chapter svg.c-status-message__icon{fill:#003f8d;vertical-align:middle}.c-article-body-section__content--separator{padding-top:40px}.c-pdf-download__link{max-height:44px}.app-article-access .u-button--primary,.app-article-access .u-button--primary:visited{color:#fff}.c-article-sidebar{display:none}@media only screen and (min-width:1024px){.c-article-sidebar{display:block}}.c-cod__form{border-radius:12px}.c-cod__label{font-size:.875rem}.c-cod .c-status-message{align-items:center;justify-content:center;margin-bottom:16px;padding-bottom:16px}@media only screen and (min-width:1024px){.c-cod .c-status-message{align-items:inherit}}.c-cod .c-status-message__icon{margin-top:4px}.c-cod .c-cod__prompt{font-size:1rem;margin-bottom:16px}.c-article-body .app-article-access,.c-book-body .app-article-access{display:block}@media only screen and (min-width:1024px){.c-article-body .app-article-access,.c-book-body .app-article-access{display:none}}.c-article-body .app-card-service{margin-bottom:32px}@media only screen and (min-width:1024px){.c-article-body .app-card-service{display:none}}.app-article-access .buybox__buy .u-button--secondary,.app-article-access .u-button--primary,.c-cod__row .u-button--primary{background-color:#025e8d;border:2px solid #025e8d;box-shadow:none;font-size:1rem;font-weight:700;gap:8px 8px;justify-content:center;line-height:1.5;padding:8px 24px}.app-article-access .buybox__buy .u-button--secondary,.app-article-access .u-button--primary:hover,.c-cod__row .u-button--primary:hover{background-color:#fff;color:#025e8d}.app-article-access .buybox__buy .u-button--secondary:hover{background-color:#025e8d;color:#fff}.buybox__buy .c-notes__text{color:#666;font-size:.875rem;padding:0 16px 8px}.c-cod__input{flex-basis:auto;width:100%}.c-article-title{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;font-size:2.25rem;font-weight:700;line-height:1.2;margin:12px 0}.c-reading-companion__figure-item figure{margin:0}@media only screen and (min-width:768px){.c-article-title{margin:16px 0}}.app-article-access{border:1px solid #c5e0f4;border-radius:12px}.app-article-access__heading{border-bottom:1px solid #c5e0f4;font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;font-size:1.125rem;font-weight:700;margin:0;padding:16px;text-align:center}.app-article-access .buybox__info svg{vertical-align:middle}.c-article-body .app-article-access p{margin-bottom:0}.app-article-access .buybox__info{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif;font-size:1rem;margin:0}.app-article-access{margin:0 0 32px}@media only screen and (min-width:1024px){.app-article-access{margin:0 0 24px}}.c-status-message{font-size:1rem}.c-article-body{font-size:1.125rem}.c-article-body dl,.c-article-body ol,.c-article-body p,.c-article-body ul{margin-bottom:32px;margin-top:0}.c-article-access-provider__text:last-of-type,.c-article-body .c-notes__text:last-of-type{margin-bottom:0}.c-article-body ol p,.c-article-body ul p{margin-bottom:16px}.c-article-section__figure-caption{font-family:Merriweather Sans,Helvetica Neue,Helvetica,Arial,sans-serif}.c-reading-companion__figure-item{border-top-color:#c5e0f4}.c-reading-companion__sticky{max-width:400px}.c-article-section .c-article-section__figure-description>*{font-size:1rem;margin-bottom:16px}.c-reading-companion__reference-item{border-top:1px solid #d5d5d5;padding:16px 0}.c-reading-companion__reference-item:first-child{padding-top:0}.c-article-share-box__button,.js .c-article-authors-search__item .c-article-button{background:0 0;border:2px solid #025e8d;border-radius:32px;box-shadow:none;color:#025e8d;font-size:1rem;font-weight:700;line-height:1.5;margin:0;padding:8px 24px;transition:all .2s ease 0s}.c-article-authors-search__item .c-article-button{width:100%}.c-pdf-download .u-button{background-color:#fff;border:2px solid #fff;color:#01324b;justify-content:center}.c-context-bar__container .c-pdf-download .u-button svg,.c-pdf-download .u-button svg{fill:currentcolor}.c-pdf-download .u-button:visited{color:#01324b}.c-pdf-download .u-button:hover{border:4px solid #01324b;box-shadow:none}.c-pdf-download .u-button:focus,.c-pdf-download .u-button:hover{background-color:#01324b}.c-pdf-download .u-button:focus svg path,.c-pdf-download .u-button:hover svg path{fill:#fff}.c-context-bar__container .c-pdf-download .u-button{background-image:none;border:2px solid;color:#fff}.c-context-bar__container .c-pdf-download .u-button:visited{color:#fff}.c-context-bar__container .c-pdf-download .u-button:hover{text-decoration:none}.c-context-bar__container .c-pdf-download .u-button:focus{box-shadow:none;outline:0;text-decoration:none}.c-context-bar__container .c-pdf-download .u-button:focus,.c-context-bar__container .c-pdf-download .u-button:hover{background-color:#fff;background-image:none;color:#01324b}.c-context-bar__container .c-pdf-download .u-button:focus svg path,.c-context-bar__container .c-pdf-download .u-button:hover svg path{fill:#01324b}.c-context-bar__container .c-pdf-download .u-button,.c-pdf-download .u-button{box-shadow:none;font-size:1rem;font-weight:700;line-height:1.5;padding:8px 24px}.c-context-bar__container .c-pdf-download .u-button{background-color:#025e8d}.c-pdf-download .u-button:hover{border:2px solid #fff}.c-pdf-download .u-button:focus,.c-pdf-download .u-button:hover{background:0 0;box-shadow:none;color:#fff}.c-context-bar__container .c-pdf-download .u-button:hover{border:2px solid #025e8d;box-shadow:none;color:#025e8d}.c-context-bar__container .c-pdf-download .u-button:focus,.c-pdf-download .u-button:focus{border:2px solid #025e8d}.c-article-share-box__button:focus:focus,.c-article__pill-button:focus:focus,.c-context-bar__container .c-pdf-download .u-button:focus:focus,.c-pdf-download .u-button:focus:focus{outline:3px solid #08c;will-change:transform}.c-pdf-download__link .u-icon{padding-top:0}.c-bibliographic-information__column button{margin-bottom:16px}.c-article-body .c-article-author-affiliation__list p,.c-article-body .c-article-author-information__list p,figure{margin:0}.c-article-share-box__button{margin-right:16px}.c-status-message--boxed{border-radius:12px}.c-article-associated-content__collection-title{font-size:1rem}.app-card-service__description,.c-article-body .app-card-service__description{color:#222;margin-bottom:0;margin-top:8px}.app-article-access__subscriptions a,.app-article-access__subscriptions a:visited,.app-book-series-listing__item a,.app-book-series-listing__item a:hover,.app-book-series-listing__item a:visited,.c-article-author-list a,.c-article-author-list a:visited,.c-article-buy-box a,.c-article-buy-box a:visited,.c-article-peer-review a,.c-article-peer-review a:visited,.c-article-satellite-subtitle a,.c-article-satellite-subtitle a:visited,.c-breadcrumbs__link,.c-breadcrumbs__link:hover,.c-breadcrumbs__link:visited{color:#000}.c-article-author-list svg{height:24px;margin:0 0 0 6px;width:24px}.c-article-header{margin-bottom:32px}@media only screen and (min-width:876px){.js .c-ad--conditional{display:block}}.u-lazy-ad-wrapper{background-color:#fff;display:none;min-height:149px}@media only screen and (min-width:876px){.u-lazy-ad-wrapper{display:block}}p.c-ad__label{margin-bottom:4px}.c-ad--728x90{background-color:#fff;border-bottom:2px solid #cedbe0} } </style> <style>@media only print, only all and (prefers-color-scheme: no-preference), only all and (prefers-color-scheme: light), only all and (prefers-color-scheme: dark) { .eds-c-header__brand img{height:24px;width:203px}.app-article-masthead__journal-link img{height:93px;width:72px}@media only screen and (min-width:769px){.app-article-masthead__journal-link img{height:161px;width:122px}} } </style> <link rel="stylesheet" data-test="critical-css-handler" data-inline-css-source="critical-css" href=/oscar-static/app-springerlink/css/core-darwin-5272567b64.css media="print" onload="this.media='all';this.onload=null"> <link rel="stylesheet" data-test="critical-css-handler" data-inline-css-source="critical-css" href="/oscar-static/app-springerlink/css/enhanced-darwin-article-72ba046d97.css" media="print" onload="this.media='only print, only all and (prefers-color-scheme: no-preference), only all and (prefers-color-scheme: light), only all and (prefers-color-scheme: dark)';this.onload=null"> <script type="text/javascript"> config = { env: 'live', site: '10698.springer.com', siteWithPath: '10698.springer.com' + window.location.pathname, twitterHashtag: '10698', cmsPrefix: 'https://studio-cms.springernature.com/studio/', publisherBrand: 'Springer', mustardcut: false }; </script> <script> window.dataLayer = [{"GA Key":"UA-26408784-1","DOI":"10.1007/s10698-017-9302-7","Page":"article","springerJournal":true,"Publishing Model":"Hybrid Access","page":{"attributes":{"environment":"live"}},"Country":"HK","japan":false,"doi":"10.1007-s10698-017-9302-7","Journal Id":10698,"Journal Title":"Foundations of Chemistry","imprint":"Springer","Keywords":"Periodic Table, Hydrogen, Fluorine, Beryllium, Noble gases, Helium, Neon, Argon, Reactivity, Electronic structure, Ionization potential, Electron affinity","kwrd":["Periodic_Table","Hydrogen","Fluorine","Beryllium","Noble_gases","Helium","Neon","Argon","Reactivity","Electronic_structure","Ionization_potential","Electron_affinity"],"Labs":"Y","ksg":"Krux.segments","kuid":"Krux.uid","Has Body":"Y","Features":[],"Open Access":"Y","hasAccess":"Y","bypassPaywall":"N","user":{"license":{"businessPartnerID":[],"businessPartnerIDString":""}},"Access Type":"open","Bpids":"","Bpnames":"","BPID":["1"],"VG Wort Identifier":"vgzm.415900-10.1007-s10698-017-9302-7","Full HTML":"Y","Subject Codes":["SCE","SCE34000","SCC00004","SC700000","SCC21001"],"pmc":["E","E34000","C00004","700000","C21001"],"session":{"authentication":{"loginStatus":"N"},"attributes":{"edition":"academic"}},"content":{"serial":{"eissn":"1572-8463","pissn":"1386-4238"},"type":"Article","category":{"pmc":{"primarySubject":"Philosophy","primarySubjectCode":"E","secondarySubjects":{"1":"Philosophy of Science","2":"Chemistry/Food Science, general","3":"History, general","4":"Physical Chemistry"},"secondarySubjectCodes":{"1":"E34000","2":"C00004","3":"700000","4":"C21001"}},"sucode":"SC21","articleType":"Article"},"attributes":{"deliveryPlatform":"oscar"}},"Event Category":"Article"}]; </script> <script data-test="springer-link-article-datalayer"> window.dataLayer = window.dataLayer || []; window.dataLayer.push({ ga4MeasurementId: 'G-B3E4QL2TPR', ga360TrackingId: 'UA-26408784-1', twitterId: 'o47a7', baiduId: 'aef3043f025ccf2305af8a194652d70b', ga4ServerUrl: 'https://collect.springer.com', imprint: 'springerlink', page: { attributes:{ featureFlags: [{ name: 'darwin-orion', active: true }, { name: 'chapter-books-recs', active: true } ], darwinAvailable: true } } }); </script> <script> (function(w, d) { w.config = w.config || {}; w.config.mustardcut = false; if (w.matchMedia && w.matchMedia('only print, only all and (prefers-color-scheme: no-preference), only all and (prefers-color-scheme: light), only all and (prefers-color-scheme: dark)').matches) { w.config.mustardcut = true; d.classList.add('js'); d.classList.remove('grade-c'); d.classList.remove('no-js'); } })(window, document.documentElement); </script> <script class="js-entry"> if (window.config.mustardcut) { (function(w, d) { window.Component = {}; window.suppressShareButton = false; window.onArticlePage = true; var currentScript = d.currentScript || d.head.querySelector('script.js-entry'); function catchNoModuleSupport() { var scriptEl = d.createElement('script'); return (!('noModule' in scriptEl) && 'onbeforeload' in scriptEl) } var headScripts = [ {'src': '/oscar-static/js/polyfill-es5-bundle-572d4fec60.js', 'async': false} ]; var bodyScripts = [ {'src': '/oscar-static/js/global-article-es5-bundle-dad1690b0d.js', 'async': false, 'module': false}, {'src': '/oscar-static/js/global-article-es6-bundle-e7d03c4cb3.js', 'async': false, 'module': true} ]; function createScript(script) { var scriptEl = d.createElement('script'); scriptEl.src = script.src; scriptEl.async = script.async; if (script.module === true) { scriptEl.type = "module"; if (catchNoModuleSupport()) { scriptEl.src = ''; } } else if (script.module === false) { scriptEl.setAttribute('nomodule', true) } if (script.charset) { scriptEl.setAttribute('charset', script.charset); } return scriptEl; } for (var i = 0; i < headScripts.length; ++i) { var scriptEl = createScript(headScripts[i]); currentScript.parentNode.insertBefore(scriptEl, currentScript.nextSibling); } d.addEventListener('DOMContentLoaded', function() { for (var i = 0; i < bodyScripts.length; ++i) { var scriptEl = createScript(bodyScripts[i]); d.body.appendChild(scriptEl); } }); // Webfont repeat view var config = w.config; if (config && config.publisherBrand && sessionStorage.fontsLoaded === 'true') { d.documentElement.className += ' webfonts-loaded'; } })(window, document); } </script> <script data-src="https://cdn.optimizely.com/js/27195530232.js" data-cc-script="C03"></script> <script data-test="gtm-head"> window.initGTM = function() { if (window.config.mustardcut) { (function (w, d, s, l, i) { w[l] = w[l] || []; w[l].push({'gtm.start': new Date().getTime(), event: 'gtm.js'}); var f = d.getElementsByTagName(s)[0], j = d.createElement(s), dl = l != 'dataLayer' ? '&l=' + l : ''; j.async = true; j.src = 'https://www.googletagmanager.com/gtm.js?id=' + i + dl; f.parentNode.insertBefore(j, f); })(window, document, 'script', 'dataLayer', 'GTM-MRVXSHQ'); } } </script> <script> (function (w, d, t) { function cc() { var h = w.location.hostname; var e = d.createElement(t), s = d.getElementsByTagName(t)[0]; if (h.indexOf('springer.com') > -1 && h.indexOf('biomedcentral.com') === -1 && h.indexOf('springeropen.com') === -1) { if (h.indexOf('link-qa.springer.com') > -1 || h.indexOf('test-www.springer.com') > -1) { e.src = 'https://cmp.springer.com/production_live/en/consent-bundle-17-52.js'; e.setAttribute('onload', "initGTM(window,document,'script','dataLayer','GTM-MRVXSHQ')"); } else { e.src = 'https://cmp.springer.com/production_live/en/consent-bundle-17-52.js'; e.setAttribute('onload', "initGTM(window,document,'script','dataLayer','GTM-MRVXSHQ')"); } } else if (h.indexOf('biomedcentral.com') > -1) { if (h.indexOf('biomedcentral.com.qa') > -1) { e.src = 'https://cmp.biomedcentral.com/production_live/en/consent-bundle-15-36.js'; e.setAttribute('onload', "initGTM(window,document,'script','dataLayer','GTM-MRVXSHQ')"); } else { e.src = 'https://cmp.biomedcentral.com/production_live/en/consent-bundle-15-36.js'; e.setAttribute('onload', "initGTM(window,document,'script','dataLayer','GTM-MRVXSHQ')"); } } else if (h.indexOf('springeropen.com') > -1) { if (h.indexOf('springeropen.com.qa') > -1) { e.src = 'https://cmp.springernature.com/production_live/en/consent-bundle-16-34.js'; e.setAttribute('onload', "initGTM(window,document,'script','dataLayer','GTM-MRVXSHQ')"); } else { e.src = 'https://cmp.springernature.com/production_live/en/consent-bundle-16-34.js'; e.setAttribute('onload', "initGTM(window,document,'script','dataLayer','GTM-MRVXSHQ')"); } } else if (h.indexOf('springernature.com') > -1) { if (h.indexOf('beta-qa.springernature.com') > -1) { e.src = 'https://cmp.springernature.com/production_live/en/consent-bundle-49-43.js'; e.setAttribute('onload', "initGTM(window,document,'script','dataLayer','GTM-NK22KLS')"); } else { e.src = 'https://cmp.springernature.com/production_live/en/consent-bundle-49-43.js'; e.setAttribute('onload', "initGTM(window,document,'script','dataLayer','GTM-NK22KLS')"); } } else { e.src = '/oscar-static/js/cookie-consent-es5-bundle-cb57c2c98a.js'; e.setAttribute('data-consent', h); } s.insertAdjacentElement('afterend', e); } cc(); })(window, document, 'script'); </script> <link rel="canonical" href="https://link.springer.com/article/10.1007/s10698-017-9302-7"/> <script type="application/ld+json">{"mainEntity":{"headline":"On the position of helium and neon in the Periodic Table of Elements","description":"Helium and neon, the two lightest noble gases, have been traditionally positioned by IUPAC in the Group 18 of the Periodic Table of Elements, together with argon, and other unreactive or moderately reactive gaseous elements (krypton, xenon, radon), and oganesson. In this account we revive the old discussion on the possible placement of helium in the Group 2, while preserving the position of neon in Group 18. We provide quantum-chemical arguments for such scenario—as well as other qualitative and quantitative arguments—and we describe previous suggestions in the literature which support it or put it into question. To this author’s own taste, He should be placed in Group 2.","datePublished":"2017-11-01T00:00:00Z","dateModified":"2017-11-01T00:00:00Z","pageStart":"191","pageEnd":"207","license":"http://creativecommons.org/licenses/by/4.0/","sameAs":"https://doi.org/10.1007/s10698-017-9302-7","keywords":["Periodic Table","Hydrogen","Fluorine","Beryllium","Noble gases","Helium","Neon","Argon","Reactivity","Electronic structure","Ionization potential","Electron affinity","Philosophy of Science","Chemistry/Food Science","general","History","Physical Chemistry"],"image":["https://media.springernature.com/lw1200/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig1_HTML.gif","https://media.springernature.com/lw1200/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig2_HTML.gif","https://media.springernature.com/lw1200/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig3a_HTML.gif","https://media.springernature.com/lw1200/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig3b_HTML.gif","https://media.springernature.com/lw1200/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig4_HTML.gif","https://media.springernature.com/lw1200/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig5_HTML.gif","https://media.springernature.com/lw1200/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig6_HTML.gif"],"isPartOf":{"name":"Foundations of Chemistry","issn":["1572-8463","1386-4238"],"volumeNumber":"20","@type":["Periodical","PublicationVolume"]},"publisher":{"name":"Springer Netherlands","logo":{"url":"https://www.springernature.com/app-sn/public/images/logo-springernature.png","@type":"ImageObject"},"@type":"Organization"},"author":[{"name":"Wojciech Grochala","affiliation":[{"name":"University of Warsaw","address":{"name":"Center of New Technologies, University of Warsaw, Warsaw, Poland","@type":"PostalAddress"},"@type":"Organization"}],"email":"w.grochala@cent.uw.edu.pl","@type":"Person"}],"isAccessibleForFree":true,"@type":"ScholarlyArticle"},"@context":"https://schema.org","@type":"WebPage"}</script> </head> <body class="" >  <noscript> <iframe src="https://www.googletagmanager.com/ns.html?id=GTM-MRVXSHQ" height="0" width="0" style="display:none;visibility:hidden"></iframe> </noscript>   <noscript data-test="gtm-body"> <iframe src="https://www.googletagmanager.com/ns.html?id=GTM-MRVXSHQ" height="0" width="0" style="display:none;visibility:hidden"></iframe> </noscript>  <div class="u-visually-hidden" aria-hidden="true" data-test="darwin-icons"> <?xml version="1.0" encoding="UTF-8"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><symbol id="icon-eds-i-accesses-medium" viewBox="0 0 24 24"><path d="M15.59 1a1 1 0 0 1 .706.291l5.41 5.385a1 1 0 0 1 .294.709v13.077c0 .674-.269 1.32-.747 1.796a2.549 2.549 0 0 1-1.798.742H15a1 1 0 0 1 0-2h4.455a.549.549 0 0 0 .387-.16.535.535 0 0 0 .158-.378V7.8L15.178 3H5.545a.543.543 0 0 0-.538.451L5 3.538v8.607a1 1 0 0 1-2 0V3.538A2.542 2.542 0 0 1 5.545 1h10.046ZM8 13c2.052 0 4.66 1.61 6.36 3.4l.124.141c.333.41.516.925.516 1.459 0 .6-.232 1.178-.64 1.599C12.666 21.388 10.054 23 8 23c-2.052 0-4.66-1.61-6.353-3.393A2.31 2.31 0 0 1 1 18c0-.6.232-1.178.64-1.6C3.34 14.61 5.948 13 8 13Zm0 2c-1.369 0-3.552 1.348-4.917 2.785A.31.31 0 0 0 3 18c0 .083.031.161.09.222C4.447 19.652 6.631 21 8 21c1.37 0 3.556-1.35 4.917-2.785A.31.31 0 0 0 13 18a.32.32 0 0 0-.048-.17l-.042-.052C11.553 16.348 9.369 15 8 15Zm0 1a2 2 0 1 1 0 4 2 2 0 0 1 0-4Z"/></symbol><symbol id="icon-eds-i-altmetric-medium" viewBox="0 0 24 24"><path d="M12 1c5.978 0 10.843 4.77 10.996 10.712l.004.306-.002.022-.002.248C22.843 18.23 17.978 23 12 23 5.925 23 1 18.075 1 12S5.925 1 12 1Zm-1.726 9.246L8.848 12.53a1 1 0 0 1-.718.461L8.003 13l-4.947.014a9.001 9.001 0 0 0 17.887-.001L16.553 13l-2.205 3.53a1 1 0 0 1-1.735-.068l-.05-.11-2.289-6.106ZM12 3a9.001 9.001 0 0 0-8.947 8.013l4.391-.012L9.652 7.47a1 1 0 0 1 1.784.179l2.288 6.104 1.428-2.283a1 1 0 0 1 .722-.462l.129-.008 4.943.012A9.001 9.001 0 0 0 12 3Z"/></symbol><symbol id="icon-eds-i-arrow-bend-down-medium" viewBox="0 0 24 24"><path d="m11.852 20.989.058.007L12 21l.075-.003.126-.017.111-.03.111-.044.098-.052.104-.074.082-.073 6-6a1 1 0 0 0-1.414-1.414L13 17.585v-12.2C13 4.075 11.964 3 10.667 3H4a1 1 0 1 0 0 2h6.667c.175 0 .333.164.333.385v12.2l-4.293-4.292a1 1 0 0 0-1.32-.083l-.094.083a1 1 0 0 0 0 1.414l6 6c.035.036.073.068.112.097l.11.071.114.054.105.035.118.025Z"/></symbol><symbol id="icon-eds-i-arrow-bend-down-small" viewBox="0 0 16 16"><path d="M1 2a1 1 0 0 0 1 1h5v8.585L3.707 8.293a1 1 0 0 0-1.32-.083l-.094.083a1 1 0 0 0 0 1.414l5 5 .063.059.093.069.081.048.105.048.104.035.105.022.096.01h.136l.122-.018.113-.03.103-.04.1-.053.102-.07.052-.043 5.04-5.037a1 1 0 1 0-1.415-1.414L9 11.583V3a2 2 0 0 0-2-2H2a1 1 0 0 0-1 1Z"/></symbol><symbol id="icon-eds-i-arrow-bend-up-medium" viewBox="0 0 24 24"><path d="m11.852 3.011.058-.007L12 3l.075.003.126.017.111.03.111.044.098.052.104.074.082.073 6 6a1 1 0 1 1-1.414 1.414L13 6.415v12.2C13 19.925 11.964 21 10.667 21H4a1 1 0 0 1 0-2h6.667c.175 0 .333-.164.333-.385v-12.2l-4.293 4.292a1 1 0 0 1-1.32.083l-.094-.083a1 1 0 0 1 0-1.414l6-6c.035-.036.073-.068.112-.097l.11-.071.114-.054.105-.035.118-.025Z"/></symbol><symbol id="icon-eds-i-arrow-bend-up-small" viewBox="0 0 16 16"><path d="M1 13.998a1 1 0 0 1 1-1h5V4.413L3.707 7.705a1 1 0 0 1-1.32.084l-.094-.084a1 1 0 0 1 0-1.414l5-5 .063-.059.093-.068.081-.05.105-.047.104-.035.105-.022L7.94 1l.136.001.122.017.113.03.103.04.1.053.102.07.052.043 5.04 5.037a1 1 0 1 1-1.415 1.414L9 4.415v8.583a2 2 0 0 1-2 2H2a1 1 0 0 1-1-1Z"/></symbol><symbol id="icon-eds-i-arrow-diagonal-medium" viewBox="0 0 24 24"><path d="M14 3h6l.075.003.126.017.111.03.111.044.098.052.096.067.09.08c.036.035.068.073.097.112l.071.11.054.114.035.105.03.148L21 4v6a1 1 0 0 1-2 0V6.414l-4.293 4.293a1 1 0 0 1-1.414-1.414L17.584 5H14a1 1 0 0 1-.993-.883L13 4a1 1 0 0 1 1-1ZM4 13a1 1 0 0 1 1 1v3.584l4.293-4.291a1 1 0 1 1 1.414 1.414L6.414 19H10a1 1 0 0 1 .993.883L11 20a1 1 0 0 1-1 1l-6.075-.003-.126-.017-.111-.03-.111-.044-.098-.052-.096-.067-.09-.08a1.01 1.01 0 0 1-.097-.112l-.071-.11-.054-.114-.035-.105-.025-.118-.007-.058L3 20v-6a1 1 0 0 1 1-1Z"/></symbol><symbol id="icon-eds-i-arrow-diagonal-small" viewBox="0 0 16 16"><path d="m2 15-.082-.004-.119-.016-.111-.03-.111-.044-.098-.052-.096-.067-.09-.08a1.008 1.008 0 0 1-.097-.112l-.071-.11-.031-.062-.034-.081-.024-.076-.025-.118-.007-.058L1 14.02V9a1 1 0 1 1 2 0v2.584l2.793-2.791a1 1 0 1 1 1.414 1.414L4.414 13H7a1 1 0 0 1 .993.883L8 14a1 1 0 0 1-1 1H2ZM14 1l.081.003.12.017.111.03.111.044.098.052.096.067.09.08c.036.035.068.073.097.112l.071.11.031.062.034.081.024.076.03.148L15 2v5a1 1 0 0 1-2 0V4.414l-2.96 2.96A1 1 0 1 1 8.626 5.96L11.584 3H9a1 1 0 0 1-.993-.883L8 2a1 1 0 0 1 1-1h5Z"/></symbol><symbol id="icon-eds-i-arrow-down-medium" viewBox="0 0 24 24"><path d="m20.707 12.728-7.99 7.98a.996.996 0 0 1-.561.281l-.157.011a.998.998 0 0 1-.788-.384l-7.918-7.908a1 1 0 0 1 1.414-1.416L11 17.576V4a1 1 0 0 1 2 0v13.598l6.293-6.285a1 1 0 0 1 1.32-.082l.095.083a1 1 0 0 1-.001 1.414Z"/></symbol><symbol id="icon-eds-i-arrow-down-small" viewBox="0 0 16 16"><path d="m1.293 8.707 6 6 .063.059.093.069.081.048.105.049.104.034.056.013.118.017L8 15l.076-.003.122-.017.113-.03.085-.032.063-.03.098-.058.06-.043.05-.043 6.04-6.037a1 1 0 0 0-1.414-1.414L9 11.583V2a1 1 0 1 0-2 0v9.585L2.707 7.293a1 1 0 0 0-1.32-.083l-.094.083a1 1 0 0 0 0 1.414Z"/></symbol><symbol id="icon-eds-i-arrow-left-medium" viewBox="0 0 24 24"><path d="m11.272 3.293-7.98 7.99a.996.996 0 0 0-.281.561L3 12.001c0 .32.15.605.384.788l7.908 7.918a1 1 0 0 0 1.416-1.414L6.424 13H20a1 1 0 0 0 0-2H6.402l6.285-6.293a1 1 0 0 0 .082-1.32l-.083-.095a1 1 0 0 0-1.414.001Z"/></symbol><symbol id="icon-eds-i-arrow-left-small" viewBox="0 0 16 16"><path d="m7.293 1.293-6 6-.059.063-.069.093-.048.081-.049.105-.034.104-.013.056-.017.118L1 8l.003.076.017.122.03.113.032.085.03.063.058.098.043.06.043.05 6.037 6.04a1 1 0 0 0 1.414-1.414L4.417 9H14a1 1 0 0 0 0-2H4.415l4.292-4.293a1 1 0 0 0 .083-1.32l-.083-.094a1 1 0 0 0-1.414 0Z"/></symbol><symbol id="icon-eds-i-arrow-right-medium" viewBox="0 0 24 24"><path d="m12.728 3.293 7.98 7.99a.996.996 0 0 1 .281.561l.011.157c0 .32-.15.605-.384.788l-7.908 7.918a1 1 0 0 1-1.416-1.414L17.576 13H4a1 1 0 0 1 0-2h13.598l-6.285-6.293a1 1 0 0 1-.082-1.32l.083-.095a1 1 0 0 1 1.414.001Z"/></symbol><symbol id="icon-eds-i-arrow-right-small" viewBox="0 0 16 16"><path d="m8.707 1.293 6 6 .059.063.069.093.048.081.049.105.034.104.013.056.017.118L15 8l-.003.076-.017.122-.03.113-.032.085-.03.063-.058.098-.043.06-.043.05-6.037 6.04a1 1 0 0 1-1.414-1.414L11.583 9H2a1 1 0 1 1 0-2h9.585L7.293 2.707a1 1 0 0 1-.083-1.32l.083-.094a1 1 0 0 1 1.414 0Z"/></symbol><symbol id="icon-eds-i-arrow-up-medium" viewBox="0 0 24 24"><path d="m3.293 11.272 7.99-7.98a.996.996 0 0 1 .561-.281L12.001 3c.32 0 .605.15.788.384l7.918 7.908a1 1 0 0 1-1.414 1.416L13 6.424V20a1 1 0 0 1-2 0V6.402l-6.293 6.285a1 1 0 0 1-1.32.082l-.095-.083a1 1 0 0 1 .001-1.414Z"/></symbol><symbol id="icon-eds-i-arrow-up-small" viewBox="0 0 16 16"><path d="m1.293 7.293 6-6 .063-.059.093-.069.081-.048.105-.049.104-.034.056-.013.118-.017L8 1l.076.003.122.017.113.03.085.032.063.03.098.058.06.043.05.043 6.04 6.037a1 1 0 0 1-1.414 1.414L9 4.417V14a1 1 0 0 1-2 0V4.415L2.707 8.707a1 1 0 0 1-1.32.083l-.094-.083a1 1 0 0 1 0-1.414Z"/></symbol><symbol id="icon-eds-i-article-medium" viewBox="0 0 24 24"><path d="M8 7a1 1 0 0 0 0 2h4a1 1 0 1 0 0-2H8ZM8 11a1 1 0 1 0 0 2h8a1 1 0 1 0 0-2H8ZM7 16a1 1 0 0 1 1-1h8a1 1 0 1 1 0 2H8a1 1 0 0 1-1-1Z"/><path d="M5.545 1A2.542 2.542 0 0 0 3 3.538v16.924A2.542 2.542 0 0 0 5.545 23h12.91A2.542 2.542 0 0 0 21 20.462V3.5A2.5 2.5 0 0 0 18.5 1H5.545ZM5 3.538C5 3.245 5.24 3 5.545 3H18.5a.5.5 0 0 1 .5.5v16.962c0 .293-.24.538-.546.538H5.545A.542.542 0 0 1 5 20.462V3.538Z" clip-rule="evenodd"/></symbol><symbol id="icon-eds-i-book-medium" viewBox="0 0 24 24"><path d="M18.5 1A2.5 2.5 0 0 1 21 3.5v12c0 1.16-.79 2.135-1.86 2.418l-.14.031V21h1a1 1 0 0 1 .993.883L21 22a1 1 0 0 1-1 1H6.5A3.5 3.5 0 0 1 3 19.5v-15A3.5 3.5 0 0 1 6.5 1h12ZM17 18H6.5a1.5 1.5 0 0 0-1.493 1.356L5 19.5A1.5 1.5 0 0 0 6.5 21H17v-3Zm1.5-15h-12A1.5 1.5 0 0 0 5 4.5v11.837l.054-.025a3.481 3.481 0 0 1 1.254-.307L6.5 16h12a.5.5 0 0 0 .492-.41L19 15.5v-12a.5.5 0 0 0-.5-.5ZM15 6a1 1 0 0 1 0 2H9a1 1 0 1 1 0-2h6Z"/></symbol><symbol id="icon-eds-i-book-series-medium" viewBox="0 0 24 24"><path fill-rule="evenodd" d="M1 3.786C1 2.759 1.857 2 2.82 2H6.18c.964 0 1.82.759 1.82 1.786V4h3.168c.668 0 1.298.364 1.616.938.158-.109.333-.195.523-.252l3.216-.965c.923-.277 1.962.204 2.257 1.187l4.146 13.82c.296.984-.307 1.957-1.23 2.234l-3.217.965c-.923.277-1.962-.203-2.257-1.187L13 10.005v10.21c0 1.04-.878 1.785-1.834 1.785H7.833c-.291 0-.575-.07-.83-.195A1.849 1.849 0 0 1 6.18 22H2.821C1.857 22 1 21.241 1 20.214V3.786ZM3 4v11h3V4H3Zm0 16v-3h3v3H3Zm15.075-.04-.814-2.712 2.874-.862.813 2.712-2.873.862Zm1.485-5.49-2.874.862-2.634-8.782 2.873-.862 2.635 8.782ZM8 20V6h3v14H8Z" clip-rule="evenodd"/></symbol><symbol id="icon-eds-i-calendar-acceptance-medium" viewBox="0 0 24 24"><path d="M17 2a1 1 0 0 1 1 1v1h1.5C20.817 4 22 5.183 22 6.5v13c0 1.317-1.183 2.5-2.5 2.5h-15C3.183 22 2 20.817 2 19.5v-13C2 5.183 3.183 4 4.5 4a1 1 0 1 1 0 2c-.212 0-.5.288-.5.5v13c0 .212.288.5.5.5h15c.212 0 .5-.288.5-.5v-13c0-.212-.288-.5-.5-.5H18v1a1 1 0 0 1-2 0V3a1 1 0 0 1 1-1Zm-.534 7.747a1 1 0 0 1 .094 1.412l-4.846 5.538a1 1 0 0 1-1.352.141l-2.77-2.076a1 1 0 0 1 1.2-1.6l2.027 1.519 4.236-4.84a1 1 0 0 1 1.411-.094ZM7.5 2a1 1 0 0 1 1 1v1H14a1 1 0 0 1 0 2H8.5v1a1 1 0 1 1-2 0V3a1 1 0 0 1 1-1Z"/></symbol><symbol id="icon-eds-i-calendar-date-medium" viewBox="0 0 24 24"><path d="M17 2a1 1 0 0 1 1 1v1h1.5C20.817 4 22 5.183 22 6.5v13c0 1.317-1.183 2.5-2.5 2.5h-15C3.183 22 2 20.817 2 19.5v-13C2 5.183 3.183 4 4.5 4a1 1 0 1 1 0 2c-.212 0-.5.288-.5.5v13c0 .212.288.5.5.5h15c.212 0 .5-.288.5-.5v-13c0-.212-.288-.5-.5-.5H18v1a1 1 0 0 1-2 0V3a1 1 0 0 1 1-1ZM8 15a1 1 0 1 1 0 2 1 1 0 0 1 0-2Zm4 0a1 1 0 1 1 0 2 1 1 0 0 1 0-2Zm-4-4a1 1 0 1 1 0 2 1 1 0 0 1 0-2Zm4 0a1 1 0 1 1 0 2 1 1 0 0 1 0-2Zm4 0a1 1 0 1 1 0 2 1 1 0 0 1 0-2ZM7.5 2a1 1 0 0 1 1 1v1H14a1 1 0 0 1 0 2H8.5v1a1 1 0 1 1-2 0V3a1 1 0 0 1 1-1Z"/></symbol><symbol id="icon-eds-i-calendar-decision-medium" viewBox="0 0 24 24"><path d="M17 2a1 1 0 0 1 1 1v1h1.5C20.817 4 22 5.183 22 6.5v13c0 1.317-1.183 2.5-2.5 2.5h-15C3.183 22 2 20.817 2 19.5v-13C2 5.183 3.183 4 4.5 4a1 1 0 1 1 0 2c-.212 0-.5.288-.5.5v13c0 .212.288.5.5.5h15c.212 0 .5-.288.5-.5v-13c0-.212-.288-.5-.5-.5H18v1a1 1 0 0 1-2 0V3a1 1 0 0 1 1-1Zm-2.935 8.246 2.686 2.645c.34.335.34.883 0 1.218l-2.686 2.645a.858.858 0 0 1-1.213-.009.854.854 0 0 1 .009-1.21l1.05-1.035H7.984a.992.992 0 0 1-.984-1c0-.552.44-1 .984-1h5.928l-1.051-1.036a.854.854 0 0 1-.085-1.121l.076-.088a.858.858 0 0 1 1.213-.009ZM7.5 2a1 1 0 0 1 1 1v1H14a1 1 0 0 1 0 2H8.5v1a1 1 0 1 1-2 0V3a1 1 0 0 1 1-1Z"/></symbol><symbol id="icon-eds-i-calendar-impact-factor-medium" viewBox="0 0 24 24"><path d="M17 2a1 1 0 0 1 1 1v1h1.5C20.817 4 22 5.183 22 6.5v13c0 1.317-1.183 2.5-2.5 2.5h-15C3.183 22 2 20.817 2 19.5v-13C2 5.183 3.183 4 4.5 4a1 1 0 1 1 0 2c-.212 0-.5.288-.5.5v13c0 .212.288.5.5.5h15c.212 0 .5-.288.5-.5v-13c0-.212-.288-.5-.5-.5H18v1a1 1 0 0 1-2 0V3a1 1 0 0 1 1-1Zm-3.2 6.924a.48.48 0 0 1 .125.544l-1.52 3.283h2.304c.27 0 .491.215.491.483a.477.477 0 0 1-.13.327l-4.18 4.484a.498.498 0 0 1-.69.031.48.48 0 0 1-.125-.544l1.52-3.284H9.291a.487.487 0 0 1-.491-.482c0-.121.047-.238.13-.327l4.18-4.484a.498.498 0 0 1 .69-.031ZM7.5 2a1 1 0 0 1 1 1v1H14a1 1 0 0 1 0 2H8.5v1a1 1 0 1 1-2 0V3a1 1 0 0 1 1-1Z"/></symbol><symbol id="icon-eds-i-call-papers-medium" viewBox="0 0 24 24"><g><path d="m20.707 2.883-1.414 1.414a1 1 0 0 0 1.414 1.414l1.414-1.414a1 1 0 0 0-1.414-1.414Z"/><path d="M6 16.054c0 2.026 1.052 2.943 3 2.943a1 1 0 1 1 0 2c-2.996 0-5-1.746-5-4.943v-1.227a4.068 4.068 0 0 1-1.83-1.189 4.553 4.553 0 0 1-.87-1.455 4.868 4.868 0 0 1-.3-1.686c0-1.17.417-2.298 1.17-3.14.38-.426.834-.767 1.338-1 .51-.237 1.06-.36 1.617-.36L6.632 6H7l7.932-2.895A2.363 2.363 0 0 1 18 5.36v9.28a2.36 2.36 0 0 1-3.069 2.25l.084.03L7 14.997H6v1.057Zm9.637-11.057a.415.415 0 0 0-.083.008L8 7.638v5.536l7.424 1.786.104.02c.035.01.072.02.109.02.2 0 .363-.16.363-.36V5.36c0-.2-.163-.363-.363-.363Zm-9.638 3h-.874a1.82 1.82 0 0 0-.625.111l-.15.063a2.128 2.128 0 0 0-.689.517c-.42.47-.661 1.123-.661 1.81 0 .34.06.678.176.992.114.308.28.585.485.816.4.447.925.691 1.464.691h.874v-5Z" clip-rule="evenodd"/><path d="M20 8.997h2a1 1 0 1 1 0 2h-2a1 1 0 1 1 0-2ZM20.707 14.293l1.414 1.414a1 1 0 0 1-1.414 1.414l-1.414-1.414a1 1 0 0 1 1.414-1.414Z"/></g></symbol><symbol id="icon-eds-i-card-medium" viewBox="0 0 24 24"><path d="M19.615 2c.315 0 .716.067 1.14.279.76.38 1.245 1.107 1.245 2.106v15.23c0 .315-.067.716-.279 1.14-.38.76-1.107 1.245-2.106 1.245H4.385a2.56 2.56 0 0 1-1.14-.279C2.485 21.341 2 20.614 2 19.615V4.385c0-.315.067-.716.279-1.14C2.659 2.485 3.386 2 4.385 2h15.23Zm0 2H4.385c-.213 0-.265.034-.317.14A.71.71 0 0 0 4 4.385v15.23c0 .213.034.265.14.317a.71.71 0 0 0 .245.068h15.23c.213 0 .265-.034.317-.14a.71.71 0 0 0 .068-.245V4.385c0-.213-.034-.265-.14-.317A.71.71 0 0 0 19.615 4ZM17 16a1 1 0 0 1 0 2H7a1 1 0 0 1 0-2h10Zm0-3a1 1 0 0 1 0 2H7a1 1 0 0 1 0-2h10Zm-.5-7A1.5 1.5 0 0 1 18 7.5v3a1.5 1.5 0 0 1-1.5 1.5h-9A1.5 1.5 0 0 1 6 10.5v-3A1.5 1.5 0 0 1 7.5 6h9ZM16 8H8v2h8V8Z"/></symbol><symbol id="icon-eds-i-cart-medium" viewBox="0 0 24 24"><path d="M5.76 1a1 1 0 0 1 .994.902L7.155 6h13.34c.18 0 .358.02.532.057l.174.045a2.5 2.5 0 0 1 1.693 3.103l-2.069 7.03c-.36 1.099-1.398 1.823-2.49 1.763H8.65c-1.272.015-2.352-.927-2.546-2.244L4.852 3H2a1 1 0 0 1-.993-.883L1 2a1 1 0 0 1 1-1h3.76Zm2.328 14.51a.555.555 0 0 0 .55.488l9.751.001a.533.533 0 0 0 .527-.357l2.059-7a.5.5 0 0 0-.48-.642H7.351l.737 7.51ZM18 19a2 2 0 1 1 0 4 2 2 0 0 1 0-4ZM8 19a2 2 0 1 1 0 4 2 2 0 0 1 0-4Z"/></symbol><symbol id="icon-eds-i-check-circle-medium" viewBox="0 0 24 24"><path d="M12 1c6.075 0 11 4.925 11 11s-4.925 11-11 11S1 18.075 1 12 5.925 1 12 1Zm0 2a9 9 0 1 0 0 18 9 9 0 0 0 0-18Zm5.125 4.72a1 1 0 0 1 .156 1.405l-6 7.5a1 1 0 0 1-1.421.143l-3-2.5a1 1 0 0 1 1.28-1.536l2.217 1.846 5.362-6.703a1 1 0 0 1 1.406-.156Z"/></symbol><symbol id="icon-eds-i-check-filled-medium" viewBox="0 0 24 24"><path d="M12 1c6.075 0 11 4.925 11 11s-4.925 11-11 11S1 18.075 1 12 5.925 1 12 1Zm5.125 6.72a1 1 0 0 0-1.406.155l-5.362 6.703-2.217-1.846a1 1 0 1 0-1.28 1.536l3 2.5a1 1 0 0 0 1.42-.143l6-7.5a1 1 0 0 0-.155-1.406Z"/></symbol><symbol id="icon-eds-i-chevron-down-medium" viewBox="0 0 24 24"><path d="M3.305 8.28a1 1 0 0 0-.024 1.415l7.495 7.762c.314.345.757.543 1.224.543.467 0 .91-.198 1.204-.522l7.515-7.783a1 1 0 1 0-1.438-1.39L12 15.845l-7.28-7.54A1 1 0 0 0 3.4 8.2l-.096.082Z"/></symbol><symbol id="icon-eds-i-chevron-down-small" viewBox="0 0 16 16"><path d="M13.692 5.278a1 1 0 0 1 .03 1.414L9.103 11.51a1.491 1.491 0 0 1-2.188.019L2.278 6.692a1 1 0 0 1 1.444-1.384L8 9.771l4.278-4.463a1 1 0 0 1 1.318-.111l.096.081Z"/></symbol><symbol id="icon-eds-i-chevron-left-medium" viewBox="0 0 24 24"><path d="M15.72 3.305a1 1 0 0 0-1.415-.024l-7.762 7.495A1.655 1.655 0 0 0 6 12c0 .467.198.91.522 1.204l7.783 7.515a1 1 0 1 0 1.39-1.438L8.155 12l7.54-7.28A1 1 0 0 0 15.8 3.4l-.082-.096Z"/></symbol><symbol id="icon-eds-i-chevron-left-small" viewBox="0 0 16 16"><path d="M10.722 2.308a1 1 0 0 0-1.414-.03L4.49 6.897a1.491 1.491 0 0 0-.019 2.188l4.838 4.637a1 1 0 1 0 1.384-1.444L6.229 8l4.463-4.278a1 1 0 0 0 .111-1.318l-.081-.096Z"/></symbol><symbol id="icon-eds-i-chevron-right-medium" viewBox="0 0 24 24"><path d="M8.28 3.305a1 1 0 0 1 1.415-.024l7.762 7.495c.345.314.543.757.543 1.224 0 .467-.198.91-.522 1.204l-7.783 7.515a1 1 0 1 1-1.39-1.438L15.845 12l-7.54-7.28A1 1 0 0 1 8.2 3.4l.082-.096Z"/></symbol><symbol id="icon-eds-i-chevron-right-small" viewBox="0 0 16 16"><path d="M5.278 2.308a1 1 0 0 1 1.414-.03l4.819 4.619a1.491 1.491 0 0 1 .019 2.188l-4.838 4.637a1 1 0 1 1-1.384-1.444L9.771 8 5.308 3.722a1 1 0 0 1-.111-1.318l.081-.096Z"/></symbol><symbol id="icon-eds-i-chevron-up-medium" viewBox="0 0 24 24"><path d="M20.695 15.72a1 1 0 0 0 .024-1.415l-7.495-7.762A1.655 1.655 0 0 0 12 6c-.467 0-.91.198-1.204.522l-7.515 7.783a1 1 0 1 0 1.438 1.39L12 8.155l7.28 7.54a1 1 0 0 0 1.319.106l.096-.082Z"/></symbol><symbol id="icon-eds-i-chevron-up-small" viewBox="0 0 16 16"><path d="M13.692 10.722a1 1 0 0 0 .03-1.414L9.103 4.49a1.491 1.491 0 0 0-2.188-.019L2.278 9.308a1 1 0 0 0 1.444 1.384L8 6.229l4.278 4.463a1 1 0 0 0 1.318.111l.096-.081Z"/></symbol><symbol id="icon-eds-i-citations-medium" viewBox="0 0 24 24"><path d="M15.59 1a1 1 0 0 1 .706.291l5.41 5.385a1 1 0 0 1 .294.709v13.077c0 .674-.269 1.32-.747 1.796a2.549 2.549 0 0 1-1.798.742h-5.843a1 1 0 1 1 0-2h5.843a.549.549 0 0 0 .387-.16.535.535 0 0 0 .158-.378V7.8L15.178 3H5.545a.543.543 0 0 0-.538.451L5 3.538v8.607a1 1 0 0 1-2 0V3.538A2.542 2.542 0 0 1 5.545 1h10.046ZM5.483 14.35c.197.26.17.62-.049.848l-.095.083-.016.011c-.36.24-.628.45-.804.634-.393.409-.59.93-.59 1.562.077-.019.192-.028.345-.028.442 0 .84.158 1.195.474.355.316.532.716.532 1.2 0 .501-.173.9-.518 1.198-.345.298-.767.446-1.266.446-.672 0-1.209-.195-1.612-.585-.403-.39-.604-.976-.604-1.757 0-.744.11-1.39.33-1.938.222-.549.49-1.009.807-1.38a4.28 4.28 0 0 1 .992-.88c.07-.043.148-.087.232-.133a.881.881 0 0 1 1.121.245Zm5 0c.197.26.17.62-.049.848l-.095.083-.016.011c-.36.24-.628.45-.804.634-.393.409-.59.93-.59 1.562.077-.019.192-.028.345-.028.442 0 .84.158 1.195.474.355.316.532.716.532 1.2 0 .501-.173.9-.518 1.198-.345.298-.767.446-1.266.446-.672 0-1.209-.195-1.612-.585-.403-.39-.604-.976-.604-1.757 0-.744.11-1.39.33-1.938.222-.549.49-1.009.807-1.38a4.28 4.28 0 0 1 .992-.88c.07-.043.148-.087.232-.133a.881.881 0 0 1 1.121.245Z"/></symbol><symbol id="icon-eds-i-clipboard-check-medium" viewBox="0 0 24 24"><path d="M14.4 1c1.238 0 2.274.865 2.536 2.024L18.5 3C19.886 3 21 4.14 21 5.535v14.93C21 21.86 19.886 23 18.5 23h-13C4.114 23 3 21.86 3 20.465V5.535C3 4.14 4.114 3 5.5 3h1.57c.27-1.147 1.3-2 2.53-2h4.8Zm4.115 4-1.59.024A2.601 2.601 0 0 1 14.4 7H9.6c-1.23 0-2.26-.853-2.53-2H5.5c-.27 0-.5.234-.5.535v14.93c0 .3.23.535.5.535h13c.27 0 .5-.234.5-.535V5.535c0-.3-.23-.535-.485-.535Zm-1.909 4.205a1 1 0 0 1 .19 1.401l-5.334 7a1 1 0 0 1-1.344.23l-2.667-1.75a1 1 0 1 1 1.098-1.672l1.887 1.238 4.769-6.258a1 1 0 0 1 1.401-.19ZM14.4 3H9.6a.6.6 0 0 0-.6.6v.8a.6.6 0 0 0 .6.6h4.8a.6.6 0 0 0 .6-.6v-.8a.6.6 0 0 0-.6-.6Z"/></symbol><symbol id="icon-eds-i-clipboard-report-medium" viewBox="0 0 24 24"><path d="M14.4 1c1.238 0 2.274.865 2.536 2.024L18.5 3C19.886 3 21 4.14 21 5.535v14.93C21 21.86 19.886 23 18.5 23h-13C4.114 23 3 21.86 3 20.465V5.535C3 4.14 4.114 3 5.5 3h1.57c.27-1.147 1.3-2 2.53-2h4.8Zm4.115 4-1.59.024A2.601 2.601 0 0 1 14.4 7H9.6c-1.23 0-2.26-.853-2.53-2H5.5c-.27 0-.5.234-.5.535v14.93c0 .3.23.535.5.535h13c.27 0 .5-.234.5-.535V5.535c0-.3-.23-.535-.485-.535Zm-2.658 10.929a1 1 0 0 1 0 2H8a1 1 0 0 1 0-2h7.857Zm0-3.929a1 1 0 0 1 0 2H8a1 1 0 0 1 0-2h7.857ZM14.4 3H9.6a.6.6 0 0 0-.6.6v.8a.6.6 0 0 0 .6.6h4.8a.6.6 0 0 0 .6-.6v-.8a.6.6 0 0 0-.6-.6Z"/></symbol><symbol id="icon-eds-i-close-medium" viewBox="0 0 24 24"><path d="M12 1c6.075 0 11 4.925 11 11s-4.925 11-11 11S1 18.075 1 12 5.925 1 12 1Zm0 2a9 9 0 1 0 0 18 9 9 0 0 0 0-18ZM8.707 7.293 12 10.585l3.293-3.292a1 1 0 0 1 1.414 1.414L13.415 12l3.292 3.293a1 1 0 0 1-1.414 1.414L12 13.415l-3.293 3.292a1 1 0 1 1-1.414-1.414L10.585 12 7.293 8.707a1 1 0 0 1 1.414-1.414Z"/></symbol><symbol id="icon-eds-i-cloud-upload-medium" viewBox="0 0 24 24"><path d="m12.852 10.011.028-.004L13 10l.075.003.126.017.086.022.136.052.098.052.104.074.082.073 3 3a1 1 0 0 1 0 1.414l-.094.083a1 1 0 0 1-1.32-.083L14 13.416V20a1 1 0 0 1-2 0v-6.586l-1.293 1.293a1 1 0 0 1-1.32.083l-.094-.083a1 1 0 0 1 0-1.414l3-3 .112-.097.11-.071.114-.054.105-.035.118-.025Zm.587-7.962c3.065.362 5.497 2.662 5.992 5.562l.013.085.207.073c2.117.782 3.496 2.845 3.337 5.097l-.022.226c-.297 2.561-2.503 4.491-5.124 4.502a1 1 0 1 1-.009-2c1.619-.007 2.967-1.186 3.147-2.733.179-1.542-.86-2.979-2.487-3.353-.512-.149-.894-.579-.981-1.165-.21-2.237-2-4.035-4.308-4.308-2.31-.273-4.497 1.06-5.25 3.19l-.049.113c-.234.468-.718.756-1.176.743-1.418.057-2.689.857-3.32 2.084a3.668 3.668 0 0 0 .262 3.798c.796 1.136 2.169 1.764 3.583 1.635a1 1 0 1 1 .182 1.992c-2.125.194-4.193-.753-5.403-2.48a5.668 5.668 0 0 1-.403-5.86c.85-1.652 2.449-2.79 4.323-3.092l.287-.039.013-.028c1.207-2.741 4.125-4.404 7.186-4.042Z"/></symbol><symbol id="icon-eds-i-collection-medium" viewBox="0 0 24 24"><path d="M21 7a1 1 0 0 1 1 1v12.5a2.5 2.5 0 0 1-2.5 2.5H8a1 1 0 0 1 0-2h11.5a.5.5 0 0 0 .5-.5V8a1 1 0 0 1 1-1Zm-5.5-5A2.5 2.5 0 0 1 18 4.5v12a2.5 2.5 0 0 1-2.5 2.5h-11A2.5 2.5 0 0 1 2 16.5v-12A2.5 2.5 0 0 1 4.5 2h11Zm0 2h-11a.5.5 0 0 0-.5.5v12a.5.5 0 0 0 .5.5h11a.5.5 0 0 0 .5-.5v-12a.5.5 0 0 0-.5-.5ZM13 13a1 1 0 0 1 0 2H7a1 1 0 0 1 0-2h6Zm0-3.5a1 1 0 0 1 0 2H7a1 1 0 0 1 0-2h6ZM13 6a1 1 0 0 1 0 2H7a1 1 0 1 1 0-2h6Z"/></symbol><symbol id="icon-eds-i-conference-series-medium" viewBox="0 0 24 24"><path fill-rule="evenodd" d="M4.5 2A2.5 2.5 0 0 0 2 4.5v11A2.5 2.5 0 0 0 4.5 18h2.37l-2.534 2.253a1 1 0 0 0 1.328 1.494L9.88 18H11v3a1 1 0 1 0 2 0v-3h1.12l4.216 3.747a1 1 0 0 0 1.328-1.494L17.13 18h2.37a2.5 2.5 0 0 0 2.5-2.5v-11A2.5 2.5 0 0 0 19.5 2h-15ZM20 6V4.5a.5.5 0 0 0-.5-.5h-15a.5.5 0 0 0-.5.5V6h16ZM4 8v7.5a.5.5 0 0 0 .5.5h15a.5.5 0 0 0 .5-.5V8H4Z" clip-rule="evenodd"/></symbol><symbol id="icon-eds-i-delivery-medium" viewBox="0 0 24 24"><path d="M8.51 20.598a3.037 3.037 0 0 1-3.02 0A2.968 2.968 0 0 1 4.161 19L3.5 19A2.5 2.5 0 0 1 1 16.5v-11A2.5 2.5 0 0 1 3.5 3h10a2.5 2.5 0 0 1 2.45 2.004L16 5h2.527c.976 0 1.855.585 2.27 1.49l2.112 4.62a1 1 0 0 1 .091.416v4.856C23 17.814 21.889 19 20.484 19h-.523a1.01 1.01 0 0 1-.121-.007 2.96 2.96 0 0 1-1.33 1.605 3.037 3.037 0 0 1-3.02 0A2.968 2.968 0 0 1 14.161 19H9.838a2.968 2.968 0 0 1-1.327 1.597Zm-2.024-3.462a.955.955 0 0 0-.481.73L5.999 18l.001.022a.944.944 0 0 0 .388.777l.098.065c.316.181.712.181 1.028 0A.97.97 0 0 0 8 17.978a.95.95 0 0 0-.486-.842 1.037 1.037 0 0 0-1.028 0Zm10 0a.955.955 0 0 0-.481.73l-.005.156a.944.944 0 0 0 .388.777l.098.065c.316.181.712.181 1.028 0a.97.97 0 0 0 .486-.886.95.95 0 0 0-.486-.842 1.037 1.037 0 0 0-1.028 0ZM21 12h-5v3.17a3.038 3.038 0 0 1 2.51.232 2.993 2.993 0 0 1 1.277 1.45l.058.155.058-.005.581-.002c.27 0 .516-.263.516-.618V12Zm-7.5-7h-10a.5.5 0 0 0-.5.5v11a.5.5 0 0 0 .5.5h.662a2.964 2.964 0 0 1 1.155-1.491l.172-.107a3.037 3.037 0 0 1 3.022 0A2.987 2.987 0 0 1 9.843 17H13.5a.5.5 0 0 0 .5-.5v-11a.5.5 0 0 0-.5-.5Zm5.027 2H16v3h4.203l-1.224-2.677a.532.532 0 0 0-.375-.316L18.527 7Z"/></symbol><symbol id="icon-eds-i-download-medium" viewBox="0 0 24 24"><path d="M22 18.5a3.5 3.5 0 0 1-3.5 3.5h-13A3.5 3.5 0 0 1 2 18.5V18a1 1 0 0 1 2 0v.5A1.5 1.5 0 0 0 5.5 20h13a1.5 1.5 0 0 0 1.5-1.5V18a1 1 0 0 1 2 0v.5Zm-3.293-7.793-6 6-.063.059-.093.069-.081.048-.105.049-.104.034-.056.013-.118.017L12 17l-.076-.003-.122-.017-.113-.03-.085-.032-.063-.03-.098-.058-.06-.043-.05-.043-6.04-6.037a1 1 0 0 1 1.414-1.414l4.294 4.29L11 3a1 1 0 0 1 2 0l.001 10.585 4.292-4.292a1 1 0 0 1 1.32-.083l.094.083a1 1 0 0 1 0 1.414Z"/></symbol><symbol id="icon-eds-i-edit-medium" viewBox="0 0 24 24"><path d="M17.149 2a2.38 2.38 0 0 1 1.699.711l2.446 2.46a2.384 2.384 0 0 1 .005 3.38L10.01 19.906a1 1 0 0 1-.434.257l-6.3 1.8a1 1 0 0 1-1.237-1.237l1.8-6.3a1 1 0 0 1 .257-.434L15.443 2.718A2.385 2.385 0 0 1 17.15 2Zm-3.874 5.689-7.586 7.536-1.234 4.319 4.318-1.234 7.54-7.582-3.038-3.039ZM17.149 4a.395.395 0 0 0-.286.126L14.695 6.28l3.029 3.029 2.162-2.173a.384.384 0 0 0 .106-.197L20 6.864c0-.103-.04-.2-.119-.278l-2.457-2.47A.385.385 0 0 0 17.149 4Z"/></symbol><symbol id="icon-eds-i-education-medium" viewBox="0 0 24 24"><path fill-rule="evenodd" d="M12.41 2.088a1 1 0 0 0-.82 0l-10 4.5a1 1 0 0 0 0 1.824L3 9.047v7.124A3.001 3.001 0 0 0 4 22a3 3 0 0 0 1-5.83V9.948l1 .45V14.5a1 1 0 0 0 .087.408L7 14.5c-.913.408-.912.41-.912.41l.001.003.003.006.007.015a1.988 1.988 0 0 0 .083.16c.054.097.131.225.236.373.21.297.53.68.993 1.057C8.351 17.292 9.824 18 12 18c2.176 0 3.65-.707 4.589-1.476.463-.378.783-.76.993-1.057a4.162 4.162 0 0 0 .319-.533l.007-.015.003-.006v-.003h.002s0-.002-.913-.41l.913.408A1 1 0 0 0 18 14.5v-4.103l4.41-1.985a1 1 0 0 0 0-1.824l-10-4.5ZM16 11.297l-3.59 1.615a1 1 0 0 1-.82 0L8 11.297v2.94a3.388 3.388 0 0 0 .677.739C9.267 15.457 10.294 16 12 16s2.734-.543 3.323-1.024a3.388 3.388 0 0 0 .677-.739v-2.94ZM4.437 7.5 12 4.097 19.563 7.5 12 10.903 4.437 7.5ZM3 19a1 1 0 1 1 2 0 1 1 0 0 1-2 0Z" clip-rule="evenodd"/></symbol><symbol id="icon-eds-i-error-diamond-medium" viewBox="0 0 24 24"><path d="M12.002 1c.702 0 1.375.279 1.871.775l8.35 8.353a2.646 2.646 0 0 1 .001 3.744l-8.353 8.353a2.646 2.646 0 0 1-3.742 0l-8.353-8.353a2.646 2.646 0 0 1 0-3.744l8.353-8.353.156-.142c.424-.362.952-.58 1.507-.625l.21-.008Zm0 2a.646.646 0 0 0-.38.123l-.093.08-8.34 8.34a.646.646 0 0 0-.18.355L3 12c0 .171.068.336.19.457l8.353 8.354a.646.646 0 0 0 .914 0l8.354-8.354a.646.646 0 0 0-.001-.914l-8.351-8.354A.646.646 0 0 0 12.002 3ZM12 14.5a1.5 1.5 0 0 1 .144 2.993L12 17.5a1.5 1.5 0 0 1 0-3ZM12 6a1 1 0 0 1 1 1v5a1 1 0 0 1-2 0V7a1 1 0 0 1 1-1Z"/></symbol><symbol id="icon-eds-i-error-filled-medium" viewBox="0 0 24 24"><path d="M12.002 1c.702 0 1.375.279 1.871.775l8.35 8.353a2.646 2.646 0 0 1 .001 3.744l-8.353 8.353a2.646 2.646 0 0 1-3.742 0l-8.353-8.353a2.646 2.646 0 0 1 0-3.744l8.353-8.353.156-.142c.424-.362.952-.58 1.507-.625l.21-.008ZM12 14.5a1.5 1.5 0 0 0 0 3l.144-.007A1.5 1.5 0 0 0 12 14.5ZM12 6a1 1 0 0 0-1 1v5a1 1 0 0 0 2 0V7a1 1 0 0 0-1-1Z"/></symbol><symbol id="icon-eds-i-external-link-medium" viewBox="0 0 24 24"><path d="M9 2a1 1 0 1 1 0 2H4.6c-.371 0-.6.209-.6.5v15c0 .291.229.5.6.5h14.8c.371 0 .6-.209.6-.5V15a1 1 0 0 1 2 0v4.5c0 1.438-1.162 2.5-2.6 2.5H4.6C3.162 22 2 20.938 2 19.5v-15C2 3.062 3.162 2 4.6 2H9Zm6 0h6l.075.003.126.017.111.03.111.044.098.052.096.067.09.08c.036.035.068.073.097.112l.071.11.054.114.035.105.03.148L22 3v6a1 1 0 0 1-2 0V5.414l-6.693 6.693a1 1 0 0 1-1.414-1.414L18.584 4H15a1 1 0 0 1-.993-.883L14 3a1 1 0 0 1 1-1Z"/></symbol><symbol id="icon-eds-i-external-link-small" viewBox="0 0 16 16"><path d="M5 1a1 1 0 1 1 0 2l-2-.001V13L13 13v-2a1 1 0 0 1 2 0v2c0 1.15-.93 2-2.067 2H3.067C1.93 15 1 14.15 1 13V3c0-1.15.93-2 2.067-2H5Zm4 0h5l.075.003.126.017.111.03.111.044.098.052.096.067.09.08.044.047.073.093.051.083.054.113.035.105.03.148L15 2v5a1 1 0 0 1-2 0V4.414L9.107 8.307a1 1 0 0 1-1.414-1.414L11.584 3H9a1 1 0 0 1-.993-.883L8 2a1 1 0 0 1 1-1Z"/></symbol><symbol id="icon-eds-i-file-download-medium" viewBox="0 0 24 24"><path d="M14.5 1a1 1 0 0 1 .707.293l5.5 5.5A1 1 0 0 1 21 7.5v12.962A2.542 2.542 0 0 1 18.455 23H5.545A2.542 2.542 0 0 1 3 20.462V3.538A2.542 2.542 0 0 1 5.545 1H14.5Zm-.415 2h-8.54A.542.542 0 0 0 5 3.538v16.924c0 .296.243.538.545.538h12.91a.542.542 0 0 0 .545-.538V7.915L14.085 3ZM12 7a1 1 0 0 1 1 1v6.585l2.293-2.292a1 1 0 0 1 1.32-.083l.094.083a1 1 0 0 1 0 1.414l-4 4a1.008 1.008 0 0 1-.112.097l-.11.071-.114.054-.105.035-.149.03L12 18l-.075-.003-.126-.017-.111-.03-.111-.044-.098-.052-.096-.067-.09-.08-4-4a1 1 0 0 1 1.414-1.414L11 14.585V8a1 1 0 0 1 1-1Z"/></symbol><symbol id="icon-eds-i-file-report-medium" viewBox="0 0 24 24"><path d="M14.5 1a1 1 0 0 1 .707.293l5.5 5.5A1 1 0 0 1 21 7.5v12.962c0 .674-.269 1.32-.747 1.796a2.549 2.549 0 0 1-1.798.742H5.545c-.674 0-1.32-.267-1.798-.742A2.535 2.535 0 0 1 3 20.462V3.538A2.542 2.542 0 0 1 5.545 1H14.5Zm-.415 2h-8.54A.542.542 0 0 0 5 3.538v16.924c0 .142.057.278.158.379.102.102.242.159.387.159h12.91a.549.549 0 0 0 .387-.16.535.535 0 0 0 .158-.378V7.915L14.085 3ZM16 17a1 1 0 0 1 0 2H8a1 1 0 0 1 0-2h8Zm0-3a1 1 0 0 1 0 2H8a1 1 0 0 1 0-2h8Zm-4.793-6.207L13 9.585l1.793-1.792a1 1 0 0 1 1.32-.083l.094.083a1 1 0 0 1 0 1.414l-2.5 2.5a1 1 0 0 1-1.414 0L10.5 9.915l-1.793 1.792a1 1 0 0 1-1.32.083l-.094-.083a1 1 0 0 1 0-1.414l2.5-2.5a1 1 0 0 1 1.414 0Z"/></symbol><symbol id="icon-eds-i-file-text-medium" viewBox="0 0 24 24"><path d="M14.5 1a1 1 0 0 1 .707.293l5.5 5.5A1 1 0 0 1 21 7.5v12.962A2.542 2.542 0 0 1 18.455 23H5.545A2.542 2.542 0 0 1 3 20.462V3.538A2.542 2.542 0 0 1 5.545 1H14.5Zm-.415 2h-8.54A.542.542 0 0 0 5 3.538v16.924c0 .296.243.538.545.538h12.91a.542.542 0 0 0 .545-.538V7.915L14.085 3ZM16 15a1 1 0 0 1 0 2H8a1 1 0 0 1 0-2h8Zm0-4a1 1 0 0 1 0 2H8a1 1 0 0 1 0-2h8Zm-5-4a1 1 0 0 1 0 2H8a1 1 0 1 1 0-2h3Z"/></symbol><symbol id="icon-eds-i-file-upload-medium" viewBox="0 0 24 24"><path d="M14.5 1a1 1 0 0 1 .707.293l5.5 5.5A1 1 0 0 1 21 7.5v12.962A2.542 2.542 0 0 1 18.455 23H5.545A2.542 2.542 0 0 1 3 20.462V3.538A2.542 2.542 0 0 1 5.545 1H14.5Zm-.415 2h-8.54A.542.542 0 0 0 5 3.538v16.924c0 .296.243.538.545.538h12.91a.542.542 0 0 0 .545-.538V7.915L14.085 3Zm-2.233 4.011.058-.007L12 7l.075.003.126.017.111.03.111.044.098.052.104.074.082.073 4 4a1 1 0 0 1 0 1.414l-.094.083a1 1 0 0 1-1.32-.083L13 10.415V17a1 1 0 0 1-2 0v-6.585l-2.293 2.292a1 1 0 0 1-1.32.083l-.094-.083a1 1 0 0 1 0-1.414l4-4 .112-.097.11-.071.114-.054.105-.035.118-.025Z"/></symbol><symbol id="icon-eds-i-filter-medium" viewBox="0 0 24 24"><path d="M21 2a1 1 0 0 1 .82 1.573L15 13.314V18a1 1 0 0 1-.31.724l-.09.076-4 3A1 1 0 0 1 9 21v-7.684L2.18 3.573a1 1 0 0 1 .707-1.567L3 2h18Zm-1.921 2H4.92l5.9 8.427a1 1 0 0 1 .172.45L11 13v6l2-1.5V13a1 1 0 0 1 .117-.469l.064-.104L19.079 4Z"/></symbol><symbol id="icon-eds-i-funding-medium" viewBox="0 0 24 24"><path fill-rule="evenodd" d="M23 8A7 7 0 1 0 9 8a7 7 0 0 0 14 0ZM9.006 12.225A4.07 4.07 0 0 0 6.12 11.02H2a.979.979 0 1 0 0 1.958h4.12c.558 0 1.094.222 1.489.617l2.207 2.288c.27.27.27.687.012.944a.656.656 0 0 1-.928 0L7.744 15.67a.98.98 0 0 0-1.386 1.384l1.157 1.158c.535.536 1.244.791 1.946.765l.041.002h6.922c.874 0 1.597.748 1.597 1.688 0 .203-.146.354-.309.354H7.755c-.487 0-.96-.178-1.339-.504L2.64 17.259a.979.979 0 0 0-1.28 1.482L5.137 22c.733.631 1.66.979 2.618.979h9.957c1.26 0 2.267-1.043 2.267-2.312 0-2.006-1.584-3.646-3.555-3.646h-4.529a2.617 2.617 0 0 0-.681-2.509l-2.208-2.287ZM16 3a5 5 0 1 0 0 10 5 5 0 0 0 0-10Zm.979 3.5a.979.979 0 1 0-1.958 0v3a.979.979 0 1 0 1.958 0v-3Z" clip-rule="evenodd"/></symbol><symbol id="icon-eds-i-hashtag-medium" viewBox="0 0 24 24"><path d="M12 1c6.075 0 11 4.925 11 11s-4.925 11-11 11S1 18.075 1 12 5.925 1 12 1Zm0 2a9 9 0 1 0 0 18 9 9 0 0 0 0-18ZM9.52 18.189a1 1 0 1 1-1.964-.378l.437-2.274H6a1 1 0 1 1 0-2h2.378l.592-3.076H6a1 1 0 0 1 0-2h3.354l.51-2.65a1 1 0 1 1 1.964.378l-.437 2.272h3.04l.51-2.65a1 1 0 1 1 1.964.378l-.438 2.272H18a1 1 0 0 1 0 2h-1.917l-.592 3.076H18a1 1 0 0 1 0 2h-2.893l-.51 2.652a1 1 0 1 1-1.964-.378l.437-2.274h-3.04l-.51 2.652Zm.895-4.652h3.04l.591-3.076h-3.04l-.591 3.076Z"/></symbol><symbol id="icon-eds-i-home-medium" viewBox="0 0 24 24"><path d="M5 22a1 1 0 0 1-1-1v-8.586l-1.293 1.293a1 1 0 0 1-1.32.083l-.094-.083a1 1 0 0 1 0-1.414l10-10a1 1 0 0 1 1.414 0l10 10a1 1 0 0 1-1.414 1.414L20 12.415V21a1 1 0 0 1-1 1H5Zm7-17.585-6 5.999V20h5v-4a1 1 0 0 1 2 0v4h5v-9.585l-6-6Z"/></symbol><symbol id="icon-eds-i-image-medium" viewBox="0 0 24 24"><path d="M19.615 2A2.385 2.385 0 0 1 22 4.385v15.23A2.385 2.385 0 0 1 19.615 22H4.385A2.385 2.385 0 0 1 2 19.615V4.385A2.385 2.385 0 0 1 4.385 2h15.23Zm0 2H4.385A.385.385 0 0 0 4 4.385v15.23c0 .213.172.385.385.385h1.244l10.228-8.76a1 1 0 0 1 1.254-.037L20 13.392V4.385A.385.385 0 0 0 19.615 4Zm-3.07 9.283L8.703 20h10.912a.385.385 0 0 0 .385-.385v-3.713l-3.455-2.619ZM9.5 6a3.5 3.5 0 1 1 0 7 3.5 3.5 0 0 1 0-7Zm0 2a1.5 1.5 0 1 0 0 3 1.5 1.5 0 0 0 0-3Z"/></symbol><symbol id="icon-eds-i-impact-factor-medium" viewBox="0 0 24 24"><path d="M16.49 2.672c.74.694.986 1.765.632 2.712l-.04.1-1.549 3.54h1.477a2.496 2.496 0 0 1 2.485 2.34l.005.163c0 .618-.23 1.21-.642 1.675l-7.147 7.961a2.48 2.48 0 0 1-3.554.165 2.512 2.512 0 0 1-.633-2.712l.042-.103L9.108 15H7.46c-1.393 0-2.379-1.11-2.455-2.369L5 12.473c0-.593.142-1.145.628-1.692l7.307-7.944a2.48 2.48 0 0 1 3.555-.165ZM14.43 4.164l-7.33 7.97c-.083.093-.101.214-.101.34 0 .277.19.526.46.526h4.163l.097-.009c.015 0 .03.003.046.009.181.078.264.32.186.5l-2.554 5.817a.512.512 0 0 0 .127.552.48.48 0 0 0 .69-.033l7.155-7.97a.513.513 0 0 0 .13-.34.497.497 0 0 0-.49-.502h-3.988a.355.355 0 0 1-.328-.497l2.555-5.844a.512.512 0 0 0-.127-.552.48.48 0 0 0-.69.033Z"/></symbol><symbol id="icon-eds-i-info-circle-medium" viewBox="0 0 24 24"><path d="M12 1c6.075 0 11 4.925 11 11s-4.925 11-11 11S1 18.075 1 12 5.925 1 12 1Zm0 2a9 9 0 1 0 0 18 9 9 0 0 0 0-18Zm0 7a1 1 0 0 1 1 1v5h1.5a1 1 0 0 1 0 2h-5a1 1 0 0 1 0-2H11v-4h-.5a1 1 0 0 1-.993-.883L9.5 11a1 1 0 0 1 1-1H12Zm0-4.5a1.5 1.5 0 0 1 .144 2.993L12 8.5a1.5 1.5 0 0 1 0-3Z"/></symbol><symbol id="icon-eds-i-info-filled-medium" viewBox="0 0 24 24"><path d="M12 1c6.075 0 11 4.925 11 11s-4.925 11-11 11S1 18.075 1 12 5.925 1 12 1Zm0 9h-1.5a1 1 0 0 0-1 1l.007.117A1 1 0 0 0 10.5 12h.5v4H9.5a1 1 0 0 0 0 2h5a1 1 0 0 0 0-2H13v-5a1 1 0 0 0-1-1Zm0-4.5a1.5 1.5 0 0 0 0 3l.144-.007A1.5 1.5 0 0 0 12 5.5Z"/></symbol><symbol id="icon-eds-i-journal-medium" viewBox="0 0 24 24"><path d="M18.5 1A2.5 2.5 0 0 1 21 3.5v14a2.5 2.5 0 0 1-2.5 2.5h-13a.5.5 0 1 0 0 1H20a1 1 0 0 1 0 2H5.5A2.5 2.5 0 0 1 3 20.5v-17A2.5 2.5 0 0 1 5.5 1h13ZM7 3H5.5a.5.5 0 0 0-.5.5v14.549l.016-.002c.104-.02.211-.035.32-.042L5.5 18H7V3Zm11.5 0H9v15h9.5a.5.5 0 0 0 .5-.5v-14a.5.5 0 0 0-.5-.5ZM16 5a1 1 0 0 1 1 1v4a1 1 0 0 1-1 1h-5a1 1 0 0 1-1-1V6a1 1 0 0 1 1-1h5Zm-1 2h-3v2h3V7Z"/></symbol><symbol id="icon-eds-i-mail-medium" viewBox="0 0 24 24"><path d="M20.462 3C21.875 3 23 4.184 23 5.619v12.762C23 19.816 21.875 21 20.462 21H3.538C2.125 21 1 19.816 1 18.381V5.619C1 4.184 2.125 3 3.538 3h16.924ZM21 8.158l-7.378 6.258a2.549 2.549 0 0 1-3.253-.008L3 8.16v10.222c0 .353.253.619.538.619h16.924c.285 0 .538-.266.538-.619V8.158ZM20.462 5H3.538c-.264 0-.5.228-.534.542l8.65 7.334c.2.165.492.165.684.007l8.656-7.342-.001-.025c-.044-.3-.274-.516-.531-.516Z"/></symbol><symbol id="icon-eds-i-mail-send-medium" viewBox="0 0 24 24"><path d="M20.444 5a2.562 2.562 0 0 1 2.548 2.37l.007.078.001.123v7.858A2.564 2.564 0 0 1 20.444 18H9.556A2.564 2.564 0 0 1 7 15.429l.001-7.977.007-.082A2.561 2.561 0 0 1 9.556 5h10.888ZM21 9.331l-5.46 3.51a1 1 0 0 1-1.08 0L9 9.332v6.097c0 .317.251.571.556.571h10.888a.564.564 0 0 0 .556-.571V9.33ZM20.444 7H9.556a.543.543 0 0 0-.32.105l5.763 3.706 5.766-3.706a.543.543 0 0 0-.32-.105ZM4.308 5a1 1 0 1 1 0 2H2a1 1 0 1 1 0-2h2.308Zm0 5.5a1 1 0 0 1 0 2H2a1 1 0 0 1 0-2h2.308Zm0 5.5a1 1 0 0 1 0 2H2a1 1 0 0 1 0-2h2.308Z"/></symbol><symbol id="icon-eds-i-mentions-medium" viewBox="0 0 24 24"><path d="m9.452 1.293 5.92 5.92 2.92-2.92a1 1 0 0 1 1.415 1.414l-2.92 2.92 5.92 5.92a1 1 0 0 1 0 1.415 10.371 10.371 0 0 1-10.378 2.584l.652 3.258A1 1 0 0 1 12 23H2a1 1 0 0 1-.874-1.486l4.789-8.62C4.194 9.074 4.9 4.43 8.038 1.292a1 1 0 0 1 1.414 0Zm-2.355 13.59L3.699 21h7.081l-.689-3.442a10.392 10.392 0 0 1-2.775-2.396l-.22-.28Zm1.69-11.427-.07.09a8.374 8.374 0 0 0 11.737 11.737l.089-.071L8.787 3.456Z"/></symbol><symbol id="icon-eds-i-menu-medium" viewBox="0 0 24 24"><path d="M21 4a1 1 0 0 1 0 2H3a1 1 0 1 1 0-2h18Zm-4 7a1 1 0 0 1 0 2H3a1 1 0 0 1 0-2h14Zm4 7a1 1 0 0 1 0 2H3a1 1 0 0 1 0-2h18Z"/></symbol><symbol id="icon-eds-i-metrics-medium" viewBox="0 0 24 24"><path d="M3 22a1 1 0 0 1-1-1V3a1 1 0 0 1 1-1h6a1 1 0 0 1 1 1v7h4V8a1 1 0 0 1 1-1h6a1 1 0 0 1 1 1v13a1 1 0 0 1-.883.993L21 22H3Zm17-2V9h-4v11h4Zm-6-8h-4v8h4v-8ZM8 4H4v16h4V4Z"/></symbol><symbol id="icon-eds-i-news-medium" viewBox="0 0 24 24"><path d="M17.384 3c.975 0 1.77.787 1.77 1.762v13.333c0 .462.354.846.815.899l.107.006.109-.006a.915.915 0 0 0 .809-.794l.006-.105V8.19a1 1 0 0 1 2 0v9.905A2.914 2.914 0 0 1 20.077 21H3.538a2.547 2.547 0 0 1-1.644-.601l-.147-.135A2.516 2.516 0 0 1 1 18.476V4.762C1 3.787 1.794 3 2.77 3h14.614Zm-.231 2H3v13.476c0 .11.035.216.1.304l.054.063c.101.1.24.157.384.157l13.761-.001-.026-.078a2.88 2.88 0 0 1-.115-.655l-.004-.17L17.153 5ZM14 15.021a.979.979 0 1 1 0 1.958H6a.979.979 0 1 1 0-1.958h8Zm0-8c.54 0 .979.438.979.979v4c0 .54-.438.979-.979.979H6A.979.979 0 0 1 5.021 12V8c0-.54.438-.979.979-.979h8Zm-.98 1.958H6.979v2.041h6.041V8.979Z"/></symbol><symbol id="icon-eds-i-newsletter-medium" viewBox="0 0 24 24"><path d="M21 10a1 1 0 0 1 1 1v9.5a2.5 2.5 0 0 1-2.5 2.5h-15A2.5 2.5 0 0 1 2 20.5V11a1 1 0 0 1 2 0v.439l8 4.888 8-4.889V11a1 1 0 0 1 1-1Zm-1 3.783-7.479 4.57a1 1 0 0 1-1.042 0l-7.48-4.57V20.5a.5.5 0 0 0 .501.5h15a.5.5 0 0 0 .5-.5v-6.717ZM15 9a1 1 0 0 1 0 2H9a1 1 0 0 1 0-2h6Zm2.5-8A2.5 2.5 0 0 1 20 3.5V9a1 1 0 0 1-2 0V3.5a.5.5 0 0 0-.5-.5h-11a.5.5 0 0 0-.5.5V9a1 1 0 1 1-2 0V3.5A2.5 2.5 0 0 1 6.5 1h11ZM15 5a1 1 0 0 1 0 2H9a1 1 0 1 1 0-2h6Z"/></symbol><symbol id="icon-eds-i-notifcation-medium" viewBox="0 0 24 24"><path d="M14 20a1 1 0 0 1 0 2h-4a1 1 0 0 1 0-2h4ZM3 18l-.133-.007c-1.156-.124-1.156-1.862 0-1.986l.3-.012C4.32 15.923 5 15.107 5 14V9.5C5 5.368 8.014 2 12 2s7 3.368 7 7.5V14c0 1.107.68 1.923 1.832 1.995l.301.012c1.156.124 1.156 1.862 0 1.986L21 18H3Zm9-14C9.17 4 7 6.426 7 9.5V14c0 .671-.146 1.303-.416 1.858L6.51 16h10.979l-.073-.142a4.192 4.192 0 0 1-.412-1.658L17 14V9.5C17 6.426 14.83 4 12 4Z"/></symbol><symbol id="icon-eds-i-publish-medium" viewBox="0 0 24 24"><g><path d="M16.296 1.291A1 1 0 0 0 15.591 1H5.545A2.542 2.542 0 0 0 3 3.538V13a1 1 0 1 0 2 0V3.538l.007-.087A.543.543 0 0 1 5.545 3h9.633L20 7.8v12.662a.534.534 0 0 1-.158.379.548.548 0 0 1-.387.159H11a1 1 0 1 0 0 2h8.455c.674 0 1.32-.267 1.798-.742A2.534 2.534 0 0 0 22 20.462V7.385a1 1 0 0 0-.294-.709l-5.41-5.385Z"/><path d="M10.762 16.647a1 1 0 0 0-1.525-1.294l-4.472 5.271-2.153-1.665a1 1 0 1 0-1.224 1.582l2.91 2.25a1 1 0 0 0 1.374-.144l5.09-6ZM16 10a1 1 0 1 1 0 2H8a1 1 0 1 1 0-2h8ZM12 7a1 1 0 0 0-1-1H8a1 1 0 1 0 0 2h3a1 1 0 0 0 1-1Z"/></g></symbol><symbol id="icon-eds-i-refresh-medium" viewBox="0 0 24 24"><g><path d="M7.831 5.636H6.032A8.76 8.76 0 0 1 9 3.631 8.549 8.549 0 0 1 12.232 3c.603 0 1.192.063 1.76.182C17.979 4.017 21 7.632 21 12a1 1 0 1 0 2 0c0-5.296-3.674-9.746-8.591-10.776A10.61 10.61 0 0 0 5 3.851V2.805a1 1 0 0 0-.987-1H4a1 1 0 0 0-1 1v3.831a1 1 0 0 0 1 1h3.831a1 1 0 0 0 .013-2h-.013ZM17.968 18.364c-1.59 1.632-3.784 2.636-6.2 2.636C6.948 21 3 16.993 3 12a1 1 0 1 0-2 0c0 6.053 4.799 11 10.768 11 2.788 0 5.324-1.082 7.232-2.85v1.045a1 1 0 1 0 2 0v-3.831a1 1 0 0 0-1-1h-3.831a1 1 0 0 0 0 2h1.799Z"/></g></symbol><symbol id="icon-eds-i-search-medium" viewBox="0 0 24 24"><path d="M11 1c5.523 0 10 4.477 10 10 0 2.4-.846 4.604-2.256 6.328l3.963 3.965a1 1 0 0 1-1.414 1.414l-3.965-3.963A9.959 9.959 0 0 1 11 21C5.477 21 1 16.523 1 11S5.477 1 11 1Zm0 2a8 8 0 1 0 0 16 8 8 0 0 0 0-16Z"/></symbol><symbol id="icon-eds-i-settings-medium" viewBox="0 0 24 24"><path d="M11.382 1h1.24a2.508 2.508 0 0 1 2.334 1.63l.523 1.378 1.59.933 1.444-.224c.954-.132 1.89.3 2.422 1.101l.095.155.598 1.066a2.56 2.56 0 0 1-.195 2.848l-.894 1.161v1.896l.92 1.163c.6.768.707 1.812.295 2.674l-.09.17-.606 1.08a2.504 2.504 0 0 1-2.531 1.25l-1.428-.223-1.589.932-.523 1.378a2.512 2.512 0 0 1-2.155 1.625L12.65 23h-1.27a2.508 2.508 0 0 1-2.334-1.63l-.524-1.379-1.59-.933-1.443.225c-.954.132-1.89-.3-2.422-1.101l-.095-.155-.598-1.066a2.56 2.56 0 0 1 .195-2.847l.891-1.161v-1.898l-.919-1.162a2.562 2.562 0 0 1-.295-2.674l.09-.17.606-1.08a2.504 2.504 0 0 1 2.531-1.25l1.43.223 1.618-.938.524-1.375.07-.167A2.507 2.507 0 0 1 11.382 1Zm.003 2a.509.509 0 0 0-.47.338l-.65 1.71a1 1 0 0 1-.434.51L7.6 6.85a1 1 0 0 1-.655.123l-1.762-.275a.497.497 0 0 0-.498.252l-.61 1.088a.562.562 0 0 0 .04.619l1.13 1.43a1 1 0 0 1 .216.62v2.585a1 1 0 0 1-.207.61L4.15 15.339a.568.568 0 0 0-.036.634l.601 1.072a.494.494 0 0 0 .484.26l1.78-.278a1 1 0 0 1 .66.126l2.2 1.292a1 1 0 0 1 .43.507l.648 1.71a.508.508 0 0 0 .467.338h1.263a.51.51 0 0 0 .47-.34l.65-1.708a1 1 0 0 1 .428-.507l2.201-1.292a1 1 0 0 1 .66-.126l1.763.275a.497.497 0 0 0 .498-.252l.61-1.088a.562.562 0 0 0-.04-.619l-1.13-1.43a1 1 0 0 1-.216-.62v-2.585a1 1 0 0 1 .207-.61l1.105-1.437a.568.568 0 0 0 .037-.634l-.601-1.072a.494.494 0 0 0-.484-.26l-1.78.278a1 1 0 0 1-.66-.126l-2.2-1.292a1 1 0 0 1-.43-.507l-.649-1.71A.508.508 0 0 0 12.62 3h-1.234ZM12 8a4 4 0 1 1 0 8 4 4 0 0 1 0-8Zm0 2a2 2 0 1 0 0 4 2 2 0 0 0 0-4Z"/></symbol><symbol id="icon-eds-i-shipping-medium" viewBox="0 0 24 24"><path d="M16.515 2c1.406 0 2.706.728 3.352 1.902l2.02 3.635.02.042.036.089.031.105.012.058.01.073.004.075v11.577c0 .64-.244 1.255-.683 1.713a2.356 2.356 0 0 1-1.701.731H4.386a2.356 2.356 0 0 1-1.702-.731 2.476 2.476 0 0 1-.683-1.713V7.948c.01-.217.083-.43.22-.6L4.2 3.905C4.833 2.755 6.089 2.032 7.486 2h9.029ZM20 9H4v10.556a.49.49 0 0 0 .075.26l.053.07a.356.356 0 0 0 .257.114h15.23c.094 0 .186-.04.258-.115a.477.477 0 0 0 .127-.33V9Zm-2 7.5a1 1 0 0 1 0 2h-4a1 1 0 0 1 0-2h4ZM16.514 4H13v3h6.3l-1.183-2.13c-.288-.522-.908-.87-1.603-.87ZM11 3.999H7.51c-.679.017-1.277.36-1.566.887L4.728 7H11V3.999Z"/></symbol><symbol id="icon-eds-i-step-guide-medium" viewBox="0 0 24 24"><path d="M11.394 9.447a1 1 0 1 0-1.788-.894l-.88 1.759-.019-.02a1 1 0 1 0-1.414 1.415l1 1a1 1 0 0 0 1.601-.26l1.5-3ZM12 11a1 1 0 0 1 1-1h3a1 1 0 1 1 0 2h-3a1 1 0 0 1-1-1ZM12 17a1 1 0 0 1 1-1h3a1 1 0 1 1 0 2h-3a1 1 0 0 1-1-1ZM10.947 14.105a1 1 0 0 1 .447 1.342l-1.5 3a1 1 0 0 1-1.601.26l-1-1a1 1 0 1 1 1.414-1.414l.02.019.879-1.76a1 1 0 0 1 1.341-.447Z"/><path d="M5.545 1A2.542 2.542 0 0 0 3 3.538v16.924A2.542 2.542 0 0 0 5.545 23h12.91A2.542 2.542 0 0 0 21 20.462V7.5a1 1 0 0 0-.293-.707l-5.5-5.5A1 1 0 0 0 14.5 1H5.545ZM5 3.538C5 3.245 5.24 3 5.545 3h8.54L19 7.914v12.547c0 .294-.24.539-.546.539H5.545A.542.542 0 0 1 5 20.462V3.538Z" clip-rule="evenodd"/></symbol><symbol id="icon-eds-i-submission-medium" viewBox="0 0 24 24"><g><path d="M5 3.538C5 3.245 5.24 3 5.545 3h9.633L20 7.8v12.662a.535.535 0 0 1-.158.379.549.549 0 0 1-.387.159H6a1 1 0 0 1-1-1v-2.5a1 1 0 1 0-2 0V20a3 3 0 0 0 3 3h13.455c.673 0 1.32-.266 1.798-.742A2.535 2.535 0 0 0 22 20.462V7.385a1 1 0 0 0-.294-.709l-5.41-5.385A1 1 0 0 0 15.591 1H5.545A2.542 2.542 0 0 0 3 3.538V7a1 1 0 0 0 2 0V3.538Z"/><path d="m13.707 13.707-4 4a1 1 0 0 1-1.414 0l-.083-.094a1 1 0 0 1 .083-1.32L10.585 14 2 14a1 1 0 1 1 0-2l8.583.001-2.29-2.294a1 1 0 0 1 1.414-1.414l4.037 4.04.043.05.043.06.059.098.03.063.031.085.03.113.017.122L14 13l-.004.087-.017.118-.013.056-.034.104-.049.105-.048.081-.07.093-.058.063Z"/></g></symbol><symbol id="icon-eds-i-table-1-medium" viewBox="0 0 24 24"><path d="M4.385 22a2.56 2.56 0 0 1-1.14-.279C2.485 21.341 2 20.614 2 19.615V4.385c0-.315.067-.716.279-1.14C2.659 2.485 3.386 2 4.385 2h15.23c.315 0 .716.067 1.14.279.76.38 1.245 1.107 1.245 2.106v15.23c0 .315-.067.716-.279 1.14-.38.76-1.107 1.245-2.106 1.245H4.385ZM4 19.615c0 .213.034.265.14.317a.71.71 0 0 0 .245.068H8v-4H4v3.615ZM20 16H10v4h9.615c.213 0 .265-.034.317-.14a.71.71 0 0 0 .068-.245V16Zm0-2v-4H10v4h10ZM4 14h4v-4H4v4ZM19.615 4H10v4h10V4.385c0-.213-.034-.265-.14-.317A.71.71 0 0 0 19.615 4ZM8 4H4.385l-.082.002c-.146.01-.19.047-.235.138A.71.71 0 0 0 4 4.385V8h4V4Z"/></symbol><symbol id="icon-eds-i-table-2-medium" viewBox="0 0 24 24"><path d="M4.384 22A2.384 2.384 0 0 1 2 19.616V4.384A2.384 2.384 0 0 1 4.384 2h15.232A2.384 2.384 0 0 1 22 4.384v15.232A2.384 2.384 0 0 1 19.616 22H4.384ZM10 15H4v4.616c0 .212.172.384.384.384H10v-5Zm5 0h-3v5h3v-5Zm5 0h-3v5h2.616a.384.384 0 0 0 .384-.384V15ZM10 9H4v4h6V9Zm5 0h-3v4h3V9Zm5 0h-3v4h3V9Zm-.384-5H4.384A.384.384 0 0 0 4 4.384V7h16V4.384A.384.384 0 0 0 19.616 4Z"/></symbol><symbol id="icon-eds-i-tag-medium" viewBox="0 0 24 24"><path d="m12.621 1.998.127.004L20.496 2a1.5 1.5 0 0 1 1.497 1.355L22 3.5l-.005 7.669c.038.456-.133.905-.447 1.206l-9.02 9.018a2.075 2.075 0 0 1-2.932 0l-6.99-6.99a2.075 2.075 0 0 1 .001-2.933L11.61 2.47c.246-.258.573-.418.881-.46l.131-.011Zm.286 2-8.885 8.886a.075.075 0 0 0 0 .106l6.987 6.988c.03.03.077.03.106 0l8.883-8.883L19.999 4l-7.092-.002ZM16 6.5a1.5 1.5 0 0 1 .144 2.993L16 9.5a1.5 1.5 0 0 1 0-3Z"/></symbol><symbol id="icon-eds-i-trash-medium" viewBox="0 0 24 24"><path d="M12 1c2.717 0 4.913 2.232 4.997 5H21a1 1 0 0 1 0 2h-1v12.5c0 1.389-1.152 2.5-2.556 2.5H6.556C5.152 23 4 21.889 4 20.5V8H3a1 1 0 1 1 0-2h4.003l.001-.051C7.114 3.205 9.3 1 12 1Zm6 7H6v12.5c0 .238.19.448.454.492l.102.008h10.888c.315 0 .556-.232.556-.5V8Zm-4 3a1 1 0 0 1 1 1v6.005a1 1 0 0 1-2 0V12a1 1 0 0 1 1-1Zm-4 0a1 1 0 0 1 1 1v6a1 1 0 0 1-2 0v-6a1 1 0 0 1 1-1Zm2-8c-1.595 0-2.914 1.32-2.996 3h5.991v-.02C14.903 4.31 13.589 3 12 3Z"/></symbol><symbol id="icon-eds-i-user-account-medium" viewBox="0 0 24 24"><path d="M12 1c6.075 0 11 4.925 11 11s-4.925 11-11 11S1 18.075 1 12 5.925 1 12 1Zm0 16c-1.806 0-3.52.994-4.664 2.698A8.947 8.947 0 0 0 12 21a8.958 8.958 0 0 0 4.664-1.301C15.52 17.994 13.806 17 12 17Zm0-14a9 9 0 0 0-6.25 15.476C7.253 16.304 9.54 15 12 15s4.747 1.304 6.25 3.475A9 9 0 0 0 12 3Zm0 3a4 4 0 1 1 0 8 4 4 0 0 1 0-8Zm0 2a2 2 0 1 0 0 4 2 2 0 0 0 0-4Z"/></symbol><symbol id="icon-eds-i-user-add-medium" viewBox="0 0 24 24"><path d="M9 1a5 5 0 1 1 0 10A5 5 0 0 1 9 1Zm0 2a3 3 0 1 0 0 6 3 3 0 0 0 0-6Zm9 10a1 1 0 0 1 1 1v3h3a1 1 0 0 1 0 2h-3v3a1 1 0 0 1-2 0v-3h-3a1 1 0 0 1 0-2h3v-3a1 1 0 0 1 1-1Zm-5.545-.15a1 1 0 1 1-.91 1.78 5.713 5.713 0 0 0-5.705.282c-1.67 1.068-2.728 2.927-2.832 4.956L3.004 20 11.5 20a1 1 0 0 1 .993.883L12.5 21a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1v-.876c.028-2.812 1.446-5.416 3.763-6.897a7.713 7.713 0 0 1 7.692-.378Z"/></symbol><symbol id="icon-eds-i-user-assign-medium" viewBox="0 0 24 24"><path d="M16.226 13.298a1 1 0 0 1 1.414-.01l.084.093a1 1 0 0 1-.073 1.32L15.39 17H22a1 1 0 0 1 0 2h-6.611l2.262 2.298a1 1 0 0 1-1.425 1.404l-3.939-4a1 1 0 0 1 0-1.404l3.94-4Zm-3.771-.449a1 1 0 1 1-.91 1.781 5.713 5.713 0 0 0-5.705.282c-1.67 1.068-2.728 2.927-2.832 4.956L3.004 20 10.5 20a1 1 0 0 1 .993.883L11.5 21a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1v-.876c.028-2.812 1.446-5.416 3.763-6.897a7.713 7.713 0 0 1 7.692-.378ZM9 1a5 5 0 1 1 0 10A5 5 0 0 1 9 1Zm0 2a3 3 0 1 0 0 6 3 3 0 0 0 0-6Z"/></symbol><symbol id="icon-eds-i-user-block-medium" viewBox="0 0 24 24"><path d="M9 1a5 5 0 1 1 0 10A5 5 0 0 1 9 1Zm0 2a3 3 0 1 0 0 6 3 3 0 0 0 0-6Zm9 10a5 5 0 1 1 0 10 5 5 0 0 1 0-10Zm-5.545-.15a1 1 0 1 1-.91 1.78 5.713 5.713 0 0 0-5.705.282c-1.67 1.068-2.728 2.927-2.832 4.956L3.004 20 11.5 20a1 1 0 0 1 .993.883L12.5 21a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1v-.876c.028-2.812 1.446-5.416 3.763-6.897a7.713 7.713 0 0 1 7.692-.378ZM15 18a3 3 0 0 0 4.294 2.707l-4.001-4c-.188.391-.293.83-.293 1.293Zm3-3c-.463 0-.902.105-1.294.293l4.001 4A3 3 0 0 0 18 15Z"/></symbol><symbol id="icon-eds-i-user-check-medium" viewBox="0 0 24 24"><path d="M9 1a5 5 0 1 1 0 10A5 5 0 0 1 9 1Zm0 2a3 3 0 1 0 0 6 3 3 0 0 0 0-6Zm13.647 12.237a1 1 0 0 1 .116 1.41l-5.091 6a1 1 0 0 1-1.375.144l-2.909-2.25a1 1 0 1 1 1.224-1.582l2.153 1.665 4.472-5.271a1 1 0 0 1 1.41-.116Zm-8.139-.977c.22.214.428.44.622.678a1 1 0 1 1-1.548 1.266 6.025 6.025 0 0 0-1.795-1.49.86.86 0 0 1-.163-.048l-.079-.036a5.721 5.721 0 0 0-2.62-.63l-.194.006c-2.76.134-5.022 2.177-5.592 4.864l-.035.175-.035.213c-.03.201-.05.405-.06.61L3.003 20 10 20a1 1 0 0 1 .993.883L11 21a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1v-.876l.005-.223.02-.356.02-.222.03-.248.022-.15c.02-.133.044-.265.071-.397.44-2.178 1.725-4.105 3.595-5.301a7.75 7.75 0 0 1 3.755-1.215l.12-.004a7.908 7.908 0 0 1 5.87 2.252Z"/></symbol><symbol id="icon-eds-i-user-delete-medium" viewBox="0 0 24 24"><path d="M9 1a5 5 0 1 1 0 10A5 5 0 0 1 9 1Zm0 2a3 3 0 1 0 0 6 3 3 0 0 0 0-6ZM4.763 13.227a7.713 7.713 0 0 1 7.692-.378 1 1 0 1 1-.91 1.781 5.713 5.713 0 0 0-5.705.282c-1.67 1.068-2.728 2.927-2.832 4.956L3.004 20H11.5a1 1 0 0 1 .993.883L12.5 21a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1v-.876c.028-2.812 1.446-5.416 3.763-6.897Zm11.421 1.543 2.554 2.553 2.555-2.553a1 1 0 0 1 1.414 1.414l-2.554 2.554 2.554 2.555a1 1 0 0 1-1.414 1.414l-2.555-2.554-2.554 2.554a1 1 0 0 1-1.414-1.414l2.553-2.555-2.553-2.554a1 1 0 0 1 1.414-1.414Z"/></symbol><symbol id="icon-eds-i-user-edit-medium" viewBox="0 0 24 24"><path d="m19.876 10.77 2.831 2.83a1 1 0 0 1 0 1.415l-7.246 7.246a1 1 0 0 1-.572.284l-3.277.446a1 1 0 0 1-1.125-1.13l.461-3.277a1 1 0 0 1 .283-.567l7.23-7.246a1 1 0 0 1 1.415-.001Zm-7.421 2.08a1 1 0 1 1-.91 1.78 5.713 5.713 0 0 0-5.705.282c-1.67 1.068-2.728 2.927-2.832 4.956L3.004 20 7.5 20a1 1 0 0 1 .993.883L8.5 21a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1v-.876c.028-2.812 1.446-5.416 3.763-6.897a7.713 7.713 0 0 1 7.692-.378Zm6.715.042-6.29 6.3-.23 1.639 1.633-.222 6.302-6.302-1.415-1.415ZM9 1a5 5 0 1 1 0 10A5 5 0 0 1 9 1Zm0 2a3 3 0 1 0 0 6 3 3 0 0 0 0-6Z"/></symbol><symbol id="icon-eds-i-user-linked-medium" viewBox="0 0 24 24"><path d="M15.65 6c.31 0 .706.066 1.122.274C17.522 6.65 18 7.366 18 8.35v12.3c0 .31-.066.706-.274 1.122-.375.75-1.092 1.228-2.076 1.228H3.35a2.52 2.52 0 0 1-1.122-.274C1.478 22.35 1 21.634 1 20.65V8.35c0-.31.066-.706.274-1.122C1.65 6.478 2.366 6 3.35 6h12.3Zm0 2-12.376.002c-.134.007-.17.04-.21.12A.672.672 0 0 0 3 8.35v12.3c0 .198.028.24.122.287.09.044.2.063.228.063h.887c.788-2.269 2.814-3.5 5.263-3.5 2.45 0 4.475 1.231 5.263 3.5h.887c.198 0 .24-.028.287-.122.044-.09.063-.2.063-.228V8.35c0-.198-.028-.24-.122-.287A.672.672 0 0 0 15.65 8ZM9.5 19.5c-1.36 0-2.447.51-3.06 1.5h6.12c-.613-.99-1.7-1.5-3.06-1.5ZM20.65 1A2.35 2.35 0 0 1 23 3.348V15.65A2.35 2.35 0 0 1 20.65 18H20a1 1 0 0 1 0-2h.65a.35.35 0 0 0 .35-.35V3.348A.35.35 0 0 0 20.65 3H8.35a.35.35 0 0 0-.35.348V4a1 1 0 1 1-2 0v-.652A2.35 2.35 0 0 1 8.35 1h12.3ZM9.5 10a3.5 3.5 0 1 1 0 7 3.5 3.5 0 0 1 0-7Zm0 2a1.5 1.5 0 1 0 0 3 1.5 1.5 0 0 0 0-3Z"/></symbol><symbol id="icon-eds-i-user-multiple-medium" viewBox="0 0 24 24"><path d="M9 1a5 5 0 1 1 0 10A5 5 0 0 1 9 1Zm6 0a5 5 0 0 1 0 10 1 1 0 0 1-.117-1.993L15 9a3 3 0 0 0 0-6 1 1 0 0 1 0-2ZM9 3a3 3 0 1 0 0 6 3 3 0 0 0 0-6Zm8.857 9.545a7.99 7.99 0 0 1 2.651 1.715A8.31 8.31 0 0 1 23 20.134V21a1 1 0 0 1-1 1h-3a1 1 0 0 1 0-2h1.995l-.005-.153a6.307 6.307 0 0 0-1.673-3.945l-.204-.209a5.99 5.99 0 0 0-1.988-1.287 1 1 0 1 1 .732-1.861Zm-3.349 1.715A8.31 8.31 0 0 1 17 20.134V21a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1v-.877c.044-4.343 3.387-7.908 7.638-8.115a7.908 7.908 0 0 1 5.87 2.252ZM9.016 14l-.285.006c-3.104.15-5.58 2.718-5.725 5.9L3.004 20h11.991l-.005-.153a6.307 6.307 0 0 0-1.673-3.945l-.204-.209A5.924 5.924 0 0 0 9.3 14.008L9.016 14Z"/></symbol><symbol id="icon-eds-i-user-notify-medium" viewBox="0 0 24 24"><path d="M9 1a5 5 0 1 1 0 10A5 5 0 0 1 9 1Zm0 2a3 3 0 1 0 0 6 3 3 0 0 0 0-6Zm10 18v1a1 1 0 0 1-2 0v-1h-3a1 1 0 0 1 0-2v-2.818C14 13.885 15.777 12 18 12s4 1.885 4 4.182V19a1 1 0 0 1 0 2h-3Zm-6.545-8.15a1 1 0 1 1-.91 1.78 5.713 5.713 0 0 0-5.705.282c-1.67 1.068-2.728 2.927-2.832 4.956L3.004 20 11.5 20a1 1 0 0 1 .993.883L12.5 21a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1v-.876c.028-2.812 1.446-5.416 3.763-6.897a7.713 7.713 0 0 1 7.692-.378ZM18 14c-1.091 0-2 .964-2 2.182V19h4v-2.818c0-1.165-.832-2.098-1.859-2.177L18 14Z"/></symbol><symbol id="icon-eds-i-user-remove-medium" viewBox="0 0 24 24"><path d="M9 1a5 5 0 1 1 0 10A5 5 0 0 1 9 1Zm0 2a3 3 0 1 0 0 6 3 3 0 0 0 0-6Zm3.455 9.85a1 1 0 1 1-.91 1.78 5.713 5.713 0 0 0-5.705.282c-1.67 1.068-2.728 2.927-2.832 4.956L3.004 20 11.5 20a1 1 0 0 1 .993.883L12.5 21a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1v-.876c.028-2.812 1.446-5.416 3.763-6.897a7.713 7.713 0 0 1 7.692-.378ZM22 17a1 1 0 0 1 0 2h-8a1 1 0 0 1 0-2h8Z"/></symbol><symbol id="icon-eds-i-user-single-medium" viewBox="0 0 24 24"><path d="M12 1a5 5 0 1 1 0 10 5 5 0 0 1 0-10Zm0 2a3 3 0 1 0 0 6 3 3 0 0 0 0-6Zm-.406 9.008a8.965 8.965 0 0 1 6.596 2.494A9.161 9.161 0 0 1 21 21.025V22a1 1 0 0 1-1 1H4a1 1 0 0 1-1-1v-.985c.05-4.825 3.815-8.777 8.594-9.007Zm.39 1.992-.299.006c-3.63.175-6.518 3.127-6.678 6.775L5 21h13.998l-.009-.268a7.157 7.157 0 0 0-1.97-4.573l-.214-.213A6.967 6.967 0 0 0 11.984 14Z"/></symbol><symbol id="icon-eds-i-warning-circle-medium" viewBox="0 0 24 24"><path d="M12 1c6.075 0 11 4.925 11 11s-4.925 11-11 11S1 18.075 1 12 5.925 1 12 1Zm0 2a9 9 0 1 0 0 18 9 9 0 0 0 0-18Zm0 11.5a1.5 1.5 0 0 1 .144 2.993L12 17.5a1.5 1.5 0 0 1 0-3ZM12 6a1 1 0 0 1 1 1v5a1 1 0 0 1-2 0V7a1 1 0 0 1 1-1Z"/></symbol><symbol id="icon-eds-i-warning-filled-medium" viewBox="0 0 24 24"><path d="M12 1c6.075 0 11 4.925 11 11s-4.925 11-11 11S1 18.075 1 12 5.925 1 12 1Zm0 13.5a1.5 1.5 0 0 0 0 3l.144-.007A1.5 1.5 0 0 0 12 14.5ZM12 6a1 1 0 0 0-1 1v5a1 1 0 0 0 2 0V7a1 1 0 0 0-1-1Z"/></symbol><symbol id="icon-chevron-left-medium" viewBox="0 0 24 24"><path d="M15.7194 3.3054C15.3358 2.90809 14.7027 2.89699 14.3054 3.28061L6.54342 10.7757C6.19804 11.09 6 11.5335 6 12C6 12.4665 6.19804 12.91 6.5218 13.204L14.3054 20.7194C14.7027 21.103 15.3358 21.0919 15.7194 20.6946C16.103 20.2973 16.0919 19.6642 15.6946 19.2806L8.155 12L15.6946 4.71939C16.0614 4.36528 16.099 3.79863 15.8009 3.40105L15.7194 3.3054Z"/></symbol><symbol id="icon-chevron-right-medium" viewBox="0 0 24 24"><path d="M8.28061 3.3054C8.66423 2.90809 9.29729 2.89699 9.6946 3.28061L17.4566 10.7757C17.802 11.09 18 11.5335 18 12C18 12.4665 17.802 12.91 17.4782 13.204L9.6946 20.7194C9.29729 21.103 8.66423 21.0919 8.28061 20.6946C7.89699 20.2973 7.90809 19.6642 8.3054 19.2806L15.845 12L8.3054 4.71939C7.93865 4.36528 7.90098 3.79863 8.19908 3.40105L8.28061 3.3054Z"/></symbol><symbol id="icon-eds-alerts" viewBox="0 0 32 32"><path d="M28 12.667c.736 0 1.333.597 1.333 1.333v13.333A3.333 3.333 0 0 1 26 30.667H6a3.333 3.333 0 0 1-3.333-3.334V14a1.333 1.333 0 1 1 2.666 0v1.252L16 21.769l10.667-6.518V14c0-.736.597-1.333 1.333-1.333Zm-1.333 5.71-9.972 6.094c-.427.26-.963.26-1.39 0l-9.972-6.094v8.956c0 .368.299.667.667.667h20a.667.667 0 0 0 .667-.667v-8.956ZM19.333 12a1.333 1.333 0 1 1 0 2.667h-6.666a1.333 1.333 0 1 1 0-2.667h6.666Zm4-10.667a3.333 3.333 0 0 1 3.334 3.334v6.666a1.333 1.333 0 1 1-2.667 0V4.667A.667.667 0 0 0 23.333 4H8.667A.667.667 0 0 0 8 4.667v6.666a1.333 1.333 0 1 1-2.667 0V4.667a3.333 3.333 0 0 1 3.334-3.334h14.666Zm-4 5.334a1.333 1.333 0 0 1 0 2.666h-6.666a1.333 1.333 0 1 1 0-2.666h6.666Z"/></symbol><symbol id="icon-eds-arrow-up" viewBox="0 0 24 24"><path fill-rule="evenodd" d="m13.002 7.408 4.88 4.88a.99.99 0 0 0 1.32.08l.09-.08c.39-.39.39-1.03 0-1.42l-6.58-6.58a1.01 1.01 0 0 0-1.42 0l-6.58 6.58a1 1 0 0 0-.09 1.32l.08.1a1 1 0 0 0 1.42-.01l4.88-4.87v11.59a.99.99 0 0 0 .88.99l.12.01c.55 0 1-.45 1-1V7.408z" class="layer"/></symbol><symbol id="icon-eds-checklist" viewBox="0 0 32 32"><path d="M19.2 1.333a3.468 3.468 0 0 1 3.381 2.699L24.667 4C26.515 4 28 5.52 28 7.38v19.906c0 1.86-1.485 3.38-3.333 3.38H7.333c-1.848 0-3.333-1.52-3.333-3.38V7.38C4 5.52 5.485 4 7.333 4h2.093A3.468 3.468 0 0 1 12.8 1.333h6.4ZM9.426 6.667H7.333c-.36 0-.666.312-.666.713v19.906c0 .401.305.714.666.714h17.334c.36 0 .666-.313.666-.714V7.38c0-.4-.305-.713-.646-.714l-2.121.033A3.468 3.468 0 0 1 19.2 9.333h-6.4a3.468 3.468 0 0 1-3.374-2.666Zm12.715 5.606c.586.446.7 1.283.253 1.868l-7.111 9.334a1.333 1.333 0 0 1-1.792.306l-3.556-2.333a1.333 1.333 0 1 1 1.463-2.23l2.517 1.651 6.358-8.344a1.333 1.333 0 0 1 1.868-.252ZM19.2 4h-6.4a.8.8 0 0 0-.8.8v1.067a.8.8 0 0 0 .8.8h6.4a.8.8 0 0 0 .8-.8V4.8a.8.8 0 0 0-.8-.8Z"/></symbol><symbol id="icon-eds-citation" viewBox="0 0 36 36"><path d="M23.25 1.5a1.5 1.5 0 0 1 1.06.44l8.25 8.25a1.5 1.5 0 0 1 .44 1.06v19.5c0 2.105-1.645 3.75-3.75 3.75H18a1.5 1.5 0 0 1 0-3h11.25c.448 0 .75-.302.75-.75V11.873L22.628 4.5H8.31a.811.811 0 0 0-.8.68l-.011.13V16.5a1.5 1.5 0 0 1-3 0V5.31A3.81 3.81 0 0 1 8.31 1.5h14.94ZM8.223 20.358a.984.984 0 0 1-.192 1.378l-.048.034c-.54.36-.942.676-1.206.951-.59.614-.885 1.395-.885 2.343.115-.028.288-.042.518-.042.662 0 1.26.237 1.791.711.533.474.799 1.074.799 1.799 0 .753-.259 1.352-.777 1.799-.518.446-1.151.669-1.9.669-1.006 0-1.812-.293-2.417-.878C3.302 28.536 3 27.657 3 26.486c0-1.115.165-2.085.496-2.907.331-.823.734-1.513 1.209-2.071.475-.558.971-.997 1.49-1.318a6.01 6.01 0 0 1 .347-.2 1.321 1.321 0 0 1 1.681.368Zm7.5 0a.984.984 0 0 1-.192 1.378l-.048.034c-.54.36-.942.676-1.206.951-.59.614-.885 1.395-.885 2.343.115-.028.288-.042.518-.042.662 0 1.26.237 1.791.711.533.474.799 1.074.799 1.799 0 .753-.259 1.352-.777 1.799-.518.446-1.151.669-1.9.669-1.006 0-1.812-.293-2.417-.878-.604-.586-.906-1.465-.906-2.636 0-1.115.165-2.085.496-2.907.331-.823.734-1.513 1.209-2.071.475-.558.971-.997 1.49-1.318a6.01 6.01 0 0 1 .347-.2 1.321 1.321 0 0 1 1.681.368Z"/></symbol><symbol id="icon-eds-i-access-indicator" viewBox="0 0 16 16"><circle cx="4.5" cy="11.5" r="3.5" style="fill:currentColor"/><path fill-rule="evenodd" d="M4 3v3a1 1 0 0 1-2 0V2.923C2 1.875 2.84 1 3.909 1h5.909a1 1 0 0 1 .713.298l3.181 3.231a1 1 0 0 1 .288.702v7.846c0 .505-.197.993-.554 1.354a1.902 1.902 0 0 1-1.355.569H10a1 1 0 1 1 0-2h2V5.64L9.4 3H4Z" clip-rule="evenodd" style="fill:#222"/></symbol><symbol id="icon-eds-i-github-medium" viewBox="0 0 24 24"><path d="M 11.964844 0 C 5.347656 0 0 5.269531 0 11.792969 C 0 17.003906 3.425781 21.417969 8.179688 22.976562 C 8.773438 23.09375 8.992188 22.722656 8.992188 22.410156 C 8.992188 22.136719 8.972656 21.203125 8.972656 20.226562 C 5.644531 20.929688 4.953125 18.820312 4.953125 18.820312 C 4.417969 17.453125 3.625 17.101562 3.625 17.101562 C 2.535156 16.378906 3.703125 16.378906 3.703125 16.378906 C 4.914062 16.457031 5.546875 17.589844 5.546875 17.589844 C 6.617188 19.386719 8.339844 18.878906 9.03125 18.566406 C 9.132812 17.804688 9.449219 17.277344 9.785156 16.984375 C 7.132812 16.710938 4.339844 15.695312 4.339844 11.167969 C 4.339844 9.878906 4.8125 8.824219 5.566406 8.003906 C 5.445312 7.710938 5.03125 6.5 5.683594 4.878906 C 5.683594 4.878906 6.695312 4.566406 8.972656 6.089844 C 9.949219 5.832031 10.953125 5.703125 11.964844 5.699219 C 12.972656 5.699219 14.003906 5.835938 14.957031 6.089844 C 17.234375 4.566406 18.242188 4.878906 18.242188 4.878906 C 18.898438 6.5 18.480469 7.710938 18.363281 8.003906 C 19.136719 8.824219 19.589844 9.878906 19.589844 11.167969 C 19.589844 15.695312 16.796875 16.691406 14.125 16.984375 C 14.558594 17.355469 14.933594 18.058594 14.933594 19.171875 C 14.933594 20.753906 14.914062 22.019531 14.914062 22.410156 C 14.914062 22.722656 15.132812 23.09375 15.726562 22.976562 C 20.480469 21.414062 23.910156 17.003906 23.910156 11.792969 C 23.929688 5.269531 18.558594 0 11.964844 0 Z M 11.964844 0 "/></symbol><symbol id="icon-eds-i-limited-access" viewBox="0 0 16 16"><path fill-rule="evenodd" d="M4 3v3a1 1 0 0 1-2 0V2.923C2 1.875 2.84 1 3.909 1h5.909a1 1 0 0 1 .713.298l3.181 3.231a1 1 0 0 1 .288.702V6a1 1 0 1 1-2 0v-.36L9.4 3H4ZM3 8a1 1 0 0 1 1 1v1a1 1 0 1 1-2 0V9a1 1 0 0 1 1-1Zm10 0a1 1 0 0 1 1 1v1a1 1 0 1 1-2 0V9a1 1 0 0 1 1-1Zm-3.5 6a1 1 0 0 1-1 1h-1a1 1 0 1 1 0-2h1a1 1 0 0 1 1 1Zm2.441-1a1 1 0 0 1 2 0c0 .73-.246 1.306-.706 1.664a1.61 1.61 0 0 1-.876.334l-.032.002H11.5a1 1 0 1 1 0-2h.441ZM4 13a1 1 0 0 0-2 0c0 .73.247 1.306.706 1.664a1.609 1.609 0 0 0 .876.334l.032.002H4.5a1 1 0 1 0 0-2H4Z" clip-rule="evenodd"/></symbol><symbol id="icon-eds-i-subjects-medium" viewBox="0 0 24 24"><g id="icon-subjects-copy" stroke="none" stroke-width="1" fill-rule="evenodd"><path d="M13.3846154,2 C14.7015971,2 15.7692308,3.06762994 15.7692308,4.38461538 L15.7692308,7.15384615 C15.7692308,8.47082629 14.7015955,9.53846154 13.3846154,9.53846154 L13.1038388,9.53925278 C13.2061091,9.85347965 13.3815528,10.1423885 13.6195822,10.3804178 C13.9722182,10.7330539 14.436524,10.9483278 14.9293854,10.9918129 L15.1153846,11 C16.2068332,11 17.2535347,11.433562 18.0254647,12.2054189 C18.6411944,12.8212361 19.0416785,13.6120766 19.1784166,14.4609738 L19.6153846,14.4615385 C20.932386,14.4615385 22,15.5291672 22,16.8461538 L22,19.6153846 C22,20.9323924 20.9323924,22 19.6153846,22 L16.8461538,22 C15.5291672,22 14.4615385,20.932386 14.4615385,19.6153846 L14.4615385,16.8461538 C14.4615385,15.5291737 15.5291737,14.4615385 16.8461538,14.4615385 L17.126925,14.460779 C17.0246537,14.1465537 16.8492179,13.857633 16.6112344,13.6196157 C16.2144418,13.2228606 15.6764136,13 15.1153846,13 C14.0239122,13 12.9771569,12.5664197 12.2053686,11.7946314 C12.1335167,11.7227795 12.0645962,11.6485444 11.9986839,11.5721119 C11.9354038,11.6485444 11.8664833,11.7227795 11.7946314,11.7946314 C11.0228431,12.5664197 9.97608778,13 8.88461538,13 C8.323576,13 7.78552852,13.2228666 7.38881294,13.6195822 C7.15078359,13.8576115 6.97533988,14.1465203 6.8730696,14.4607472 L7.15384615,14.4615385 C8.47082629,14.4615385 9.53846154,15.5291737 9.53846154,16.8461538 L9.53846154,19.6153846 C9.53846154,20.932386 8.47083276,22 7.15384615,22 L4.38461538,22 C3.06762347,22 2,20.9323876 2,19.6153846 L2,16.8461538 C2,15.5291721 3.06762994,14.4615385 4.38461538,14.4615385 L4.8215823,14.4609378 C4.95831893,13.6120029 5.3588057,12.8211623 5.97459937,12.2053686 C6.69125996,11.488708 7.64500941,11.0636656 8.6514968,11.0066017 L8.88461538,11 C9.44565477,11 9.98370225,10.7771334 10.3804178,10.3804178 C10.6184472,10.1423885 10.7938909,9.85347965 10.8961612,9.53925278 L10.6153846,9.53846154 C9.29840448,9.53846154 8.23076923,8.47082629 8.23076923,7.15384615 L8.23076923,4.38461538 C8.23076923,3.06762994 9.29840286,2 10.6153846,2 L13.3846154,2 Z M7.15384615,16.4615385 L4.38461538,16.4615385 C4.17220099,16.4615385 4,16.63374 4,16.8461538 L4,19.6153846 C4,19.8278134 4.17218833,20 4.38461538,20 L7.15384615,20 C7.36626945,20 7.53846154,19.8278103 7.53846154,19.6153846 L7.53846154,16.8461538 C7.53846154,16.6337432 7.36625679,16.4615385 7.15384615,16.4615385 Z M19.6153846,16.4615385 L16.8461538,16.4615385 C16.6337432,16.4615385 16.4615385,16.6337432 16.4615385,16.8461538 L16.4615385,19.6153846 C16.4615385,19.8278103 16.6337306,20 16.8461538,20 L19.6153846,20 C19.8278229,20 20,19.8278229 20,19.6153846 L20,16.8461538 C20,16.6337306 19.8278103,16.4615385 19.6153846,16.4615385 Z M13.3846154,4 L10.6153846,4 C10.4029708,4 10.2307692,4.17220099 10.2307692,4.38461538 L10.2307692,7.15384615 C10.2307692,7.36625679 10.402974,7.53846154 10.6153846,7.53846154 L13.3846154,7.53846154 C13.597026,7.53846154 13.7692308,7.36625679 13.7692308,7.15384615 L13.7692308,4.38461538 C13.7692308,4.17220099 13.5970292,4 13.3846154,4 Z" id="Shape" fill-rule="nonzero"/></g></symbol><symbol id="icon-eds-small-arrow-left" viewBox="0 0 16 17"><path stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M14 8.092H2m0 0L8 2M2 8.092l6 6.035"/></symbol><symbol id="icon-eds-small-arrow-right" viewBox="0 0 16 16"><g fill-rule="evenodd" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"><path d="M2 8.092h12M8 2l6 6.092M8 14.127l6-6.035"/></g></symbol><symbol id="icon-orcid-logo" viewBox="0 0 40 40"><path fill-rule="evenodd" d="M12.281 10.453c.875 0 1.578-.719 1.578-1.578 0-.86-.703-1.578-1.578-1.578-.875 0-1.578.703-1.578 1.578 0 .86.703 1.578 1.578 1.578Zm-1.203 18.641h2.406V12.359h-2.406v16.735Z"/><path fill-rule="evenodd" d="M17.016 12.36h6.5c6.187 0 8.906 4.421 8.906 8.374 0 4.297-3.36 8.375-8.875 8.375h-6.531V12.36Zm6.234 14.578h-3.828V14.53h3.703c4.688 0 6.828 2.844 6.828 6.203 0 2.063-1.25 6.203-6.703 6.203Z" clip-rule="evenodd"/></symbol></svg> </div> <a class="c-skip-link" href="#main">Skip to main content</a> <header class="eds-c-header" data-eds-c-header> <div class="eds-c-header__container" data-eds-c-header-expander-anchor> <div class="eds-c-header__brand"> <a href="https://link.springer.com" data-test=springerlink-logo data-track="click_imprint_logo" data-track-context="unified header" data-track-action="click logo link" data-track-category="unified header" data-track-label="link" > <img src="/oscar-static/images/darwin/header/img/logo-springer-nature-link-3149409f62.svg" alt="Springer Nature Link"> </a> </div> <a class="c-header__link eds-c-header__link" id="identity-account-widget" href='https://idp.springer.com/auth/personal/springernature?redirect_uri=https://link.springer.com/article/10.1007/s10698-017-9302-7?'><span class="eds-c-header__widget-fragment-title">Log in</span></a> </div> <nav class="eds-c-header__nav" aria-label="header navigation"> <div class="eds-c-header__nav-container"> <div class="eds-c-header__item eds-c-header__item--menu"> <a href="#eds-c-header-nav" class="eds-c-header__link" data-eds-c-header-expander> <svg class="eds-c-header__icon" width="24" height="24" aria-hidden="true" focusable="false"> <use xlink:href="#icon-eds-i-menu-medium"></use> </svg><span>Menu</span> </a> </div> <div class="eds-c-header__item eds-c-header__item--inline-links"> <a class="eds-c-header__link" href="https://link.springer.com/journals/" data-track="nav_find_a_journal" data-track-context="unified header" data-track-action="click find a journal" data-track-category="unified header" data-track-label="link" > Find a journal </a> <a class="eds-c-header__link" href="https://www.springernature.com/gp/authors" data-track="nav_how_to_publish" data-track-context="unified header" data-track-action="click publish with us link" data-track-category="unified header" data-track-label="link" > Publish with us </a> <a class="eds-c-header__link" href="https://link.springernature.com/home/" data-track="nav_track_your_research" data-track-context="unified header" data-track-action="click track your research" data-track-category="unified header" data-track-label="link" > Track your research </a> </div> <div class="eds-c-header__link-container"> <div class="eds-c-header__item eds-c-header__item--divider"> <a href="#eds-c-header-popup-search" class="eds-c-header__link" data-eds-c-header-expander data-eds-c-header-test-search-btn> <svg class="eds-c-header__icon" width="24" height="24" aria-hidden="true" focusable="false"> <use xlink:href="#icon-eds-i-search-medium"></use> </svg><span>Search</span> </a> </div> <div id="ecommerce-header-cart-icon-link" class="eds-c-header__item ecommerce-cart" style="display:inline-block"> <a class="eds-c-header__link" href="https://order.springer.com/public/cart" style="appearance:none;border:none;background:none;color:inherit;position:relative"> <svg id="eds-i-cart" class="eds-c-header__icon" xmlns="http://www.w3.org/2000/svg" height="24" width="24" viewBox="0 0 24 24" aria-hidden="true" focusable="false"> <path fill="currentColor" fill-rule="nonzero" d="M2 1a1 1 0 0 0 0 2l1.659.001 2.257 12.808a2.599 2.599 0 0 0 2.435 2.185l.167.004 9.976-.001a2.613 2.613 0 0 0 2.61-1.748l.03-.106 1.755-7.82.032-.107a2.546 2.546 0 0 0-.311-1.986l-.108-.157a2.604 2.604 0 0 0-2.197-1.076L6.042 5l-.56-3.17a1 1 0 0 0-.864-.82l-.12-.007L2.001 1ZM20.35 6.996a.63.63 0 0 1 .54.26.55.55 0 0 1 .082.505l-.028.1L19.2 15.63l-.022.05c-.094.177-.282.299-.526.317l-10.145.002a.61.61 0 0 1-.618-.515L6.394 6.999l13.955-.003ZM18 19a2 2 0 1 0 0 4 2 2 0 0 0 0-4ZM8 19a2 2 0 1 0 0 4 2 2 0 0 0 0-4Z"></path> </svg><span>Cart</span><span class="cart-info" style="display:none;position:absolute;top:10px;right:45px;background-color:#C65301;color:#fff;width:18px;height:18px;font-size:11px;border-radius:50%;line-height:17.5px;text-align:center"></span></a> <script>(function () { var exports = {}; if (window.fetch) { "use strict"; Object.defineProperty(exports, "__esModule", { value: true }); exports.headerWidgetClientInit = void 0; var headerWidgetClientInit = function (getCartInfo) { document.body.addEventListener("updatedCart", function () { updateCartIcon(); }, false); return updateCartIcon(); function updateCartIcon() { return getCartInfo() .then(function (res) { return res.json(); }) .then(refreshCartState) .catch(function (_) { }); } function refreshCartState(json) { var indicator = document.querySelector("#ecommerce-header-cart-icon-link .cart-info"); /* istanbul ignore else */ if (indicator && json.itemCount) { indicator.style.display = 'block'; indicator.textContent = json.itemCount > 9 ? '9+' : json.itemCount.toString(); var moreThanOneItem = json.itemCount > 1; indicator.setAttribute('title', "there ".concat(moreThanOneItem ? "are" : "is", " ").concat(json.itemCount, " item").concat(moreThanOneItem ? "s" : "", " in your cart")); } return json; } }; exports.headerWidgetClientInit = headerWidgetClientInit; headerWidgetClientInit( function () { return window.fetch("https://cart.springer.com/cart-info", { credentials: "include", headers: { Accept: "application/json" } }) } ) }})()</script> </div> </div> </div> </nav> </header> <article lang="en" id="main" class="app-masthead__colour-default"> <section class="app-masthead " aria-label="article masthead"> <div class="app-masthead__container"> <div class="app-article-masthead u-sans-serif js-context-bar-sticky-point-masthead" data-track-component="article" data-test="masthead-component"> <div class="app-article-masthead__info"> <nav aria-label="breadcrumbs" data-test="breadcrumbs"> <ol class="c-breadcrumbs c-breadcrumbs--contrast" itemscope itemtype="https://schema.org/BreadcrumbList"> <li class="c-breadcrumbs__item" id="breadcrumb0" itemprop="itemListElement" itemscope="" itemtype="https://schema.org/ListItem"> <a href="/" class="c-breadcrumbs__link" itemprop="item" data-track="click_breadcrumb" data-track-context="article page" data-track-category="article" data-track-action="breadcrumbs" data-track-label="breadcrumb1"><span itemprop="name">Home</span></a><meta itemprop="position" content="1"> <svg class="c-breadcrumbs__chevron" role="img" aria-hidden="true" focusable="false" width="10" height="10" viewBox="0 0 10 10"> <path d="m5.96738168 4.70639573 2.39518594-2.41447274c.37913917-.38219212.98637524-.38972225 1.35419292-.01894278.37750606.38054586.37784436.99719163-.00013556 1.37821513l-4.03074001 4.06319683c-.37758093.38062133-.98937525.38100976-1.367372-.00003075l-4.03091981-4.06337806c-.37759778-.38063832-.38381821-.99150444-.01600053-1.3622839.37750607-.38054587.98772445-.38240057 1.37006824.00302197l2.39538588 2.4146743.96295325.98624457z" fill-rule="evenodd" transform="matrix(0 -1 1 0 0 10)"/> </svg> </li> <li class="c-breadcrumbs__item" id="breadcrumb1" itemprop="itemListElement" itemscope="" itemtype="https://schema.org/ListItem"> <a href="/journal/10698" class="c-breadcrumbs__link" itemprop="item" data-track="click_breadcrumb" data-track-context="article page" data-track-category="article" data-track-action="breadcrumbs" data-track-label="breadcrumb2"><span itemprop="name">Foundations of Chemistry</span></a><meta itemprop="position" content="2"> <svg class="c-breadcrumbs__chevron" role="img" aria-hidden="true" focusable="false" width="10" height="10" viewBox="0 0 10 10"> <path d="m5.96738168 4.70639573 2.39518594-2.41447274c.37913917-.38219212.98637524-.38972225 1.35419292-.01894278.37750606.38054586.37784436.99719163-.00013556 1.37821513l-4.03074001 4.06319683c-.37758093.38062133-.98937525.38100976-1.367372-.00003075l-4.03091981-4.06337806c-.37759778-.38063832-.38381821-.99150444-.01600053-1.3622839.37750607-.38054587.98772445-.38240057 1.37006824.00302197l2.39538588 2.4146743.96295325.98624457z" fill-rule="evenodd" transform="matrix(0 -1 1 0 0 10)"/> </svg> </li> <li class="c-breadcrumbs__item" id="breadcrumb2" itemprop="itemListElement" itemscope="" itemtype="https://schema.org/ListItem"> <span itemprop="name">Article</span><meta itemprop="position" content="3"> </li> </ol> </nav> <h1 class="c-article-title" data-test="article-title" data-article-title="">On the position of helium and neon in the Periodic Table of Elements</h1> <ul class="c-article-identifiers"> <li class="c-article-identifiers__item"> <a href="https://www.springernature.com/gp/open-research/about/the-fundamentals-of-open-access-and-open-research" data-track="click" data-track-action="open access" data-track-label="link" class="u-color-open-access" data-test="open-access">Open access</a> </li> <li class="c-article-identifiers__item"> Published: <time datetime="2017-11-01">01 November 2017</time> </li> </ul> <ul class="c-article-identifiers c-article-identifiers--cite-list"> <li class="c-article-identifiers__item"> <span data-test="journal-volume">Volume 20</span>, pages 191–207, (<span data-test="article-publication-year">2018</span>) </li> <li class="c-article-identifiers__item c-article-identifiers__item--cite"> <a href="#citeas" data-track="click" data-track-action="cite this article" data-track-category="article body" data-track-label="link">Cite this article</a> </li> </ul> <div class="app-article-masthead__buttons" data-test="download-article-link-wrapper" data-track-context="masthead"> <div class="c-pdf-container"> <div class="c-pdf-download u-clear-both u-mb-16"> <a href="/content/pdf/10.1007/s10698-017-9302-7.pdf" class="u-button u-button--full-width u-button--primary u-justify-content-space-between c-pdf-download__link" data-article-pdf="true" data-readcube-pdf-url="true" data-test="pdf-link" data-draft-ignore="true" data-track="content_download" data-track-type="article pdf download" data-track-action="download pdf" data-track-label="button" data-track-external download> <span class="c-pdf-download__text">Download PDF</span> <svg aria-hidden="true" focusable="false" width="16" height="16" class="u-icon"><use xlink:href="#icon-eds-i-download-medium"/></svg> </a> </div> </div> <p class="app-article-masthead__access"> <svg width="16" height="16" focusable="false" role="img" aria-hidden="true"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-check-filled-medium"></use></svg> You have full access to this <a href="https://www.springernature.com/gp/open-research/about/the-fundamentals-of-open-access-and-open-research" data-track="click" data-track-action="open access" data-track-label="link">open access</a> article</p> </div> </div> <div class="app-article-masthead__brand"> <a href="/journal/10698" class="app-article-masthead__journal-link" data-track="click_journal_home" data-track-action="journal homepage" data-track-context="article page" data-track-label="link"> <picture> <source type="image/webp" media="(min-width: 768px)" width="120" height="159" srcset="https://media.springernature.com/w120/springer-static/cover-hires/journal/10698?as=webp, https://media.springernature.com/w316/springer-static/cover-hires/journal/10698?as=webp 2x"> <img width="72" height="95" src="https://media.springernature.com/w72/springer-static/cover-hires/journal/10698?as=webp" srcset="https://media.springernature.com/w144/springer-static/cover-hires/journal/10698?as=webp 2x" alt=""> </picture> <span class="app-article-masthead__journal-title">Foundations of Chemistry</span> </a> <a href="https://link.springer.com/journal/10698/aims-and-scope" class="app-article-masthead__submission-link" data-track="click_aims_and_scope" data-track-action="aims and scope" data-track-context="article page" data-track-label="link"> Aims and scope <svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-arrow-right-medium"></use></svg> </a> <a href="https://submission.springernature.com/new-submission/10698/3" class="app-article-masthead__submission-link" data-track="click_submit_manuscript" data-track-context="article masthead on springerlink article page" data-track-action="submit manuscript" data-track-label="link"> Submit manuscript <svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-arrow-right-medium"></use></svg> </a> </div> </div> </div> </section> <div class="c-article-main u-container u-mt-24 u-mb-32 l-with-sidebar" id="main-content" data-component="article-container"> <main class="u-serif js-main-column" data-track-component="article body"> <div class="c-context-bar u-hide" data-test="context-bar" data-context-bar aria-hidden="true"> <div class="c-context-bar__container u-container"> <div class="c-context-bar__title"> On the position of helium and neon in the Periodic Table of Elements </div> <div data-test="inCoD" data-track-context="sticky banner"> <div class="c-pdf-container"> <div class="c-pdf-download u-clear-both u-mb-16"> <a href="/content/pdf/10.1007/s10698-017-9302-7.pdf" class="u-button u-button--full-width u-button--primary u-justify-content-space-between c-pdf-download__link" data-article-pdf="true" data-readcube-pdf-url="true" data-test="pdf-link" data-draft-ignore="true" data-track="content_download" data-track-type="article pdf download" data-track-action="download pdf" data-track-label="button" data-track-external download> <span class="c-pdf-download__text">Download PDF</span> <svg aria-hidden="true" focusable="false" width="16" height="16" class="u-icon"><use xlink:href="#icon-eds-i-download-medium"/></svg> </a> </div> </div> </div> </div> </div> <div class="c-article-header"> <header> <ul class="c-article-author-list c-article-author-list--short" data-test="authors-list" data-component-authors-activator="authors-list"><li class="c-article-author-list__item"><a data-test="author-name" data-track="click" data-track-action="open author" data-track-label="link" href="#auth-Wojciech-Grochala-Aff1" data-author-popup="auth-Wojciech-Grochala-Aff1" data-author-search="Grochala, Wojciech" data-corresp-id="c1">Wojciech Grochala<svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-mail-medium"></use></svg></a><sup class="u-js-hide"><a href="#Aff1">1</a></sup> </li></ul> <div data-test="article-metrics"> <ul class="app-article-metrics-bar u-list-reset"> <li class="app-article-metrics-bar__item"> <p class="app-article-metrics-bar__count"><svg class="u-icon app-article-metrics-bar__icon" width="24" height="24" aria-hidden="true" focusable="false"> <use xlink:href="#icon-eds-i-accesses-medium"></use> </svg>27k <span class="app-article-metrics-bar__label">Accesses</span></p> </li> <li class="app-article-metrics-bar__item"> <p class="app-article-metrics-bar__count"><svg class="u-icon app-article-metrics-bar__icon" width="24" height="24" aria-hidden="true" focusable="false"> <use xlink:href="#icon-eds-i-citations-medium"></use> </svg>18 <span class="app-article-metrics-bar__label">Citations</span></p> </li> <li class="app-article-metrics-bar__item"> <p class="app-article-metrics-bar__count"><svg class="u-icon app-article-metrics-bar__icon" width="24" height="24" aria-hidden="true" focusable="false"> <use xlink:href="#icon-eds-i-altmetric-medium"></use> </svg>3 <span class="app-article-metrics-bar__label">Altmetric</span></p> </li> <li class="app-article-metrics-bar__item app-article-metrics-bar__item--metrics"> <p class="app-article-metrics-bar__details"><a href="/article/10.1007/s10698-017-9302-7/metrics" data-track="click" data-track-action="view metrics" data-track-label="link" rel="nofollow">Explore all metrics <svg class="u-icon app-article-metrics-bar__arrow-icon" width="24" height="24" aria-hidden="true" focusable="false"> <use xlink:href="#icon-eds-i-arrow-right-medium"></use> </svg></a></p> </li> </ul> </div> <div class="u-mt-32"> </div> </header> </div> <div data-article-body="true" data-track-component="article body" class="c-article-body"> <section aria-labelledby="Abs1" data-title="Abstract" lang="en"><div class="c-article-section" id="Abs1-section"><h2 class="c-article-section__title js-section-title js-c-reading-companion-sections-item" id="Abs1">Abstract</h2><div class="c-article-section__content" id="Abs1-content"><p>Helium and neon, the two lightest noble gases, have been traditionally positioned by IUPAC in the Group 18 of the Periodic Table of Elements, together with argon, and other unreactive or moderately reactive gaseous elements (krypton, xenon, radon), and oganesson. In this account we revive the old discussion on the possible placement of helium in the Group 2, while preserving the position of neon in Group 18. We provide quantum-chemical arguments for such scenario—as well as other qualitative and quantitative arguments—and we describe previous suggestions in the literature which support it or put it into question. To this author’s own taste, He should be placed in Group 2.</p></div></div></section> <div data-test="cobranding-download"> </div> <section aria-labelledby="inline-recommendations" data-title="Inline Recommendations" class="c-article-recommendations" data-track-component="inline-recommendations"> <h3 class="c-article-recommendations-title" id="inline-recommendations">Similar content being viewed by others</h3> <div class="c-article-recommendations-list"> <div class="c-article-recommendations-list__item"> <article class="c-article-recommendations-card" itemscope itemtype="http://schema.org/ScholarlyArticle"> <div class="c-article-recommendations-card__img"><img src="https://media.springernature.com/w92h120/springer-static/cover-hires/book/978-3-319-15123-6?as=webp" loading="lazy" alt=""></div> <div class="c-article-recommendations-card__main"> <h3 class="c-article-recommendations-card__heading" itemprop="name headline"> <a class="c-article-recommendations-card__link" itemprop="url" href="https://link.springer.com/10.1007/978-3-319-15123-6_1?fromPaywallRec=false" data-track="select_recommendations_1" data-track-context="inline recommendations" data-track-action="click recommendations inline - 1" data-track-label="10.1007/978-3-319-15123-6_1">What Is Helium? </a> </h3> <div class="c-article-meta-recommendations" data-test="recommendation-info"> <span class="c-article-meta-recommendations__item-type">Chapter</span> <span class="c-article-meta-recommendations__date">© 2015</span> </div> </div> </article> </div> <div class="c-article-recommendations-list__item"> <article class="c-article-recommendations-card" itemscope itemtype="http://schema.org/ScholarlyArticle"> <div class="c-article-recommendations-card__img"><img src="https://media.springernature.com/w215h120/springer-static/image/art%3A10.1007%2Fs10698-023-09496-5/MediaObjects/10698_2023_9496_Fig1_HTML.png" loading="lazy" alt=""></div> <div class="c-article-recommendations-card__main"> <h3 class="c-article-recommendations-card__heading" itemprop="name headline"> <a class="c-article-recommendations-card__link" itemprop="url" href="https://link.springer.com/10.1007/s10698-023-09496-5?fromPaywallRec=false" data-track="select_recommendations_2" data-track-context="inline recommendations" data-track-action="click recommendations inline - 2" data-track-label="10.1007/s10698-023-09496-5">Hydrogen over helium: A philosophical position </a> </h3> <div class="c-article-meta-recommendations" data-test="recommendation-info"> <span class="c-article-meta-recommendations__item-type">Article</span> <span class="c-article-meta-recommendations__date">17 April 2024</span> </div> </div> </article> </div> <div class="c-article-recommendations-list__item"> <article class="c-article-recommendations-card" itemscope itemtype="http://schema.org/ScholarlyArticle"> <div class="c-article-recommendations-card__img"><img src="https://media.springernature.com/w92h120/springer-static/cover-hires/book/978-3-319-15123-6?as=webp" loading="lazy" alt=""></div> <div class="c-article-recommendations-card__main"> <h3 class="c-article-recommendations-card__heading" itemprop="name headline"> <a class="c-article-recommendations-card__link" itemprop="url" href="https://link.springer.com/10.1007/978-3-319-15123-6_4?fromPaywallRec=false" data-track="select_recommendations_3" data-track-context="inline recommendations" data-track-action="click recommendations inline - 3" data-track-label="10.1007/978-3-319-15123-6_4">Helium on Earth </a> </h3> <div class="c-article-meta-recommendations" data-test="recommendation-info"> <span class="c-article-meta-recommendations__item-type">Chapter</span> <span class="c-article-meta-recommendations__date">© 2015</span> </div> </div> </article> </div> </div> </section> <script> window.dataLayer = window.dataLayer || []; window.dataLayer.push({ recommendations: { recommender: 'semantic', model: 'specter', policy_id: 'NA', timestamp: 1732686005, embedded_user: 'null' } }); </script> <div class="app-card-service" data-test="article-checklist-banner"> <div> <a class="app-card-service__link" data-track="click_presubmission_checklist" data-track-context="article page top of reading companion" data-track-category="pre-submission-checklist" data-track-action="clicked article page checklist banner test 2 old version" data-track-label="link" href="https://beta.springernature.com/pre-submission?journalId=10698" data-test="article-checklist-banner-link"> <span class="app-card-service__link-text">Use our pre-submission checklist</span> <svg class="app-card-service__link-icon" aria-hidden="true" focusable="false"><use xlink:href="#icon-eds-i-arrow-right-small"></use></svg> </a> <p class="app-card-service__description">Avoid common mistakes on your manuscript.</p> </div> <div class="app-card-service__icon-container"> <svg class="app-card-service__icon" aria-hidden="true" focusable="false"> <use xlink:href="#icon-eds-i-clipboard-check-medium"></use> </svg> </div> </div> <div class="main-content"> <div class="c-article-section__content c-article-section__content--separator"><p>The traditional depiction of the periodic system, which has been taught to this author in primary school in the 1980s, has been the so-called short version (SPT), with the division to A (main group) and B (transition metal) Group elements (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig1">1</a> top). This version follows to some extent the early formulation by Mendeleyev, and introduces Group VIII containing Fe, Co, Ni, and their heavier analogues. Here, noble gases stand out as Group 0, to emphasize lack of room for them in the original Mendeleyev’s formulation; this happily coincides with their null (or weak at best) bond-forming ability. On the other hand, the Periodic Table recommended to this author during education in the comprehensive school a decade later was the so-called long version (LPT), with the transition metal elements clearly separated from the main group ones (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig1">1</a> bottom, Roman numerals). Here, the A and B Groups still persisted. Finally, the freshman years of the 1990s brought another, more subtle, modification: the giant Periodic Table depicted in the Grand Aula of the Chemistry Faculty of the University of Warsaw corresponds to a long version, with noble gases placed in the last Group of the chart, the Group numbering now running from 1 to 18 in Arabic rather than Roman numbers (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig1">1</a> bottom, Arabic numerals). Now, the old Group VIII encompasses three modern Groups: 8, 9 and 10. This version of the Table survived in the main didactic room to this day, except for a few elements being given their new IUPAC-recommended names (Francl <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009" title="Francl, M.: Table manners. Nat. Chem. 1(2), 97–98 (2009)" href="/article/10.1007/s10698-017-9302-7#ref-CR22" id="ref-link-section-d55432524e321">2009</a>). It may seem that with the naming of the last superheavy elements in 2016, the history of the formulation of the Periodic Chart is closed, or at least it will rest until the new Period is opened due to a synthesis of a Z > 118 element (Seaborg <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1969" title="Seaborg, G.T.: Prospects for further considerable extension of the periodic table. J. Chem. Educ. 46(10), 626–634 (1969)" href="/article/10.1007/s10698-017-9302-7#ref-CR82" id="ref-link-section-d55432524e324">1969</a>; Pyykkö <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2011" title="Pyykkö, P.: A suggested periodic table up to Z ≤ 172, based on Dirac-Fock calculations on atoms and ions. Phys. Chem. Chem. Phys. 13(1), 161–168 (2011)" href="/article/10.1007/s10698-017-9302-7#ref-CR73" id="ref-link-section-d55432524e328">2011</a>).</p><div class="c-article-section__figure js-c-reading-companion-figures-item" data-test="figure" data-container-section="figure" id="figure-1" data-title="Fig. 1"><figure><figcaption><b id="Fig1" class="c-article-section__figure-caption" data-test="figure-caption-text">Fig. 1</b></figcaption><div class="c-article-section__figure-content"><div class="c-article-section__figure-item"><a class="c-article-section__figure-link" data-test="img-link" data-track="click" data-track-label="image" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/1" rel="nofollow"><picture><source type="image/webp" srcset="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig1_HTML.gif?as=webp"><img aria-describedby="Fig1" src="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig1_HTML.gif" alt="figure 1" loading="lazy"></picture></a></div><div class="c-article-section__figure-description" data-test="bottom-caption" id="figure-1-desc"><p>Top: Short version of the Periodic Chart. Bottom: Long version</p></div></div><div class="u-text-right u-hide-print"><a class="c-article__pill-button" data-test="article-link" data-track="click" data-track-label="button" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/1" data-track-dest="link:Figure1 Full size image" aria-label="Full size image figure 1" rel="nofollow"><span>Full size image</span><svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-chevron-right-small"></use></svg></a></div></figure></div> </div><div class="c-article-section__content"><p>In all versions routinely used today in the universities worldwide, helium, the Z = 2 element, is been placed together with other “noble” gases, i.e. neon, argon, krypton, xenon, radon (and Ununoptium, <i>i.e.</i> the recently named oganesson). However, this has not necessarily been the case, if other historically important formulations of the Periodic Table are taken into consideration. Specifically, the so-called left-step form of the periodic table, LSPT (Janet <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1928a" title="Janet, C.: Essais de classification hélicoïdale des éléments chimiques. Imprimerie Départementale de l’Oise, Beauvais (1928a)" href="/article/10.1007/s10698-017-9302-7#ref-CR44" id="ref-link-section-d55432524e355">1928a</a>, <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference b" title="Janet, C.: La classification hélicoïdale des éléments chimiques. Imprimerie Départementale de l’Oise, Beauvais (1928b)" href="/article/10.1007/s10698-017-9302-7#ref-CR45" id="ref-link-section-d55432524e358">b</a>, <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1929" title="Janet, C.: The helicoidal classification of the elements. Chem. News 138(372–374), 388–393 (1929)" href="/article/10.1007/s10698-017-9302-7#ref-CR46" id="ref-link-section-d55432524e361">1929</a>; Tarantola <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2000" title="Tarantola, A.: A Periodic Table of the elements, based on the electronic structure of the atoms. (2000) chemistry/0009002" href="/article/10.1007/s10698-017-9302-7#ref-CR91" id="ref-link-section-d55432524e364">2000</a>; Scerri <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2005a" title="Scerri, E.R.: Presenting the left-step periodic table. Educ. Chem. 42, 135–136 (2005a)" href="/article/10.1007/s10698-017-9302-7#ref-CR78" id="ref-link-section-d55432524e368">2005a</a>; Stewart <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2010" title="Stewart, P.J.: Charles Janet: unrecognized genius of the periodic system. Found. Chem. 12(1), 5–15 (2010)" href="/article/10.1007/s10698-017-9302-7#ref-CR84" id="ref-link-section-d55432524e371">2010</a>) organizes elements according to the orbital filling (instead of theoretical maximum valence) and is sometimes used by physicists (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig2">2</a> top and middle). This version strongly emphasizes the electronic structure of isolated atoms in the gas phase, and the fact of existence of the <i>s</i>, <i>p</i>, <i>d</i>, and <i>f</i> blocks of the Periodic Table. Scerri’s modifications of the Table (both “symmetric traditional”, and LSPT, for the latter see Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig2">2</a> bottom) seem to lose this feature while they position helium in a traditional way above neon (Scerri <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009" title="Scerri, E.R.: Periodic change. Chem. World 3, 46–49 (2009)" href="/article/10.1007/s10698-017-9302-7#ref-CR81" id="ref-link-section-d55432524e393">2009</a>). In addition, in these versions, hydrogen is placed together with halogens (we will return later to <i>pros</i> and <i>cons</i> of that).</p><div class="c-article-section__figure js-c-reading-companion-figures-item" data-test="figure" data-container-section="figure" id="figure-2" data-title="Fig. 2"><figure><figcaption><b id="Fig2" class="c-article-section__figure-caption" data-test="figure-caption-text">Fig. 2</b></figcaption><div class="c-article-section__figure-content"><div class="c-article-section__figure-item"><a class="c-article-section__figure-link" data-test="img-link" data-track="click" data-track-label="image" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/2" rel="nofollow"><picture><source type="image/webp" srcset="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig2_HTML.gif?as=webp"><img aria-describedby="Fig2" src="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig2_HTML.gif" alt="figure 2" loading="lazy"></picture></a></div><div class="c-article-section__figure-description" data-test="bottom-caption" id="figure-2-desc"><p>Top and Middle: two left-step forms of the Periodic Chart. Bottom: Scerri’s modification</p></div></div><div class="u-text-right u-hide-print"><a class="c-article__pill-button" data-test="article-link" data-track="click" data-track-label="button" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/2" data-track-dest="link:Figure2 Full size image" aria-label="Full size image figure 2" rel="nofollow"><span>Full size image</span><svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-chevron-right-small"></use></svg></a></div></figure></div> </div><div class="c-article-section__content"><p>Stowe’s physicist’s periodic table (PPT) goes even further than Janet into linking of the placement of elements with the modern understanding of the electronic structure of atoms, and it is three-dimensional with the three axes representing the principal quantum number, orbital quantum number, and orbital magnetic quantum number (Stowe <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1989" title="Stowe, T.: A Physicist’s Chart of the Chemical Elements. Instruments Research and Industry Inc., Wyncote (1989)" href="/article/10.1007/s10698-017-9302-7#ref-CR89" id="ref-link-section-d55432524e423">1989</a>). Here, helium is again a Group 2 element, with neon falling into the same vertical Column as argon and heavier noble gases (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig3">3</a> top). Similarly, the versions proposed by Le Cornec (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig3">3</a> middle) (Le Cornec <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2002" title="Le Cornec, H.: The distribution of atomic ionization potentials reveals an unexpected Periodic Table. physchem/0201007 (2002)" href="/article/10.1007/s10698-017-9302-7#ref-CR53" id="ref-link-section-d55432524e432">2002</a>), and Tarantola (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig3">3</a> bottom) (Tarantola <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2002" title="Tarantola, A.: The Periodic Table of the elements and the ionization potentials. (2002) physchem/0201017" href="/article/10.1007/s10698-017-9302-7#ref-CR92" id="ref-link-section-d55432524e439">2002</a>), while they strive to take into account the first ionization potential of isolated atoms in the gas phase, they prefer placing helium above beryllium rather than above neon. This is also the case for all versions of the Chart proposed by Górski (not shown here) (Górski <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2001" title="Górski, A.W.: Morphological classification of chemical structural units. Pol. J. Chem. 75, 159–207 (2001)" href="/article/10.1007/s10698-017-9302-7#ref-CR30" id="ref-link-section-d55432524e442">2001</a>). The selection between various forms of the Table is a matter of personal idiosyncrasies, as correctly noticed by many authors (for interesting comment, <i>cf.</i> Schwarz 2016<sup><a href="#Fn1"><span class="u-visually-hidden">Footnote </span>1</a></sup>). </p><div class="c-article-section__figure js-c-reading-companion-figures-item" data-test="figure" data-container-section="figure" id="figure-3" data-title="Fig. 3"><figure><figcaption><b id="Fig3" class="c-article-section__figure-caption" data-test="figure-caption-text">Fig. 3</b></figcaption><div class="c-article-section__figure-content"><div class="c-article-section__figure-item"><a class="c-article-section__figure-link" data-test="img-link" data-track="click" data-track-label="image" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/3" rel="nofollow"><picture><source type="image/webp" srcset="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig3a_HTML.gif?as=webp"><img aria-describedby="Fig3" src="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig3a_HTML.gif" alt="figure 3" loading="lazy"></picture><picture><source type="image/webp" srcset="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig3b_HTML.gif?as=webp"><img aria-describedby="Fig3" src="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig3b_HTML.gif" alt="figure 3" loading="lazy"></picture></a></div><div class="c-article-section__figure-description" data-test="bottom-caption" id="figure-3-desc"><p>Top: Stowe’s, Middle: Le Cornec’s, and Bottom: Tarantola’s versions of the Periodic Chart</p></div></div><div class="u-text-right u-hide-print"><a class="c-article__pill-button" data-test="article-link" data-track="click" data-track-label="button" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/3" data-track-dest="link:Figure3 Full size image" aria-label="Full size image figure 3" rel="nofollow"><span>Full size image</span><svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-chevron-right-small"></use></svg></a></div></figure></div> </div><div class="c-article-section__content"><p>A question naturally arises: <i>Is there any preferred placement of helium in the Periodic Table?</i> This question may, but does not need to be linked to an even more important one: <i>Is there any supreme (“most correct”) version of the Table itself</i>? (<i>cf.</i> Scerri <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2007" title="Scerri, E.R.: The Periodic Table: Its Story and Its Significance. Oxford University Press, Oxford (2007)" href="/article/10.1007/s10698-017-9302-7#ref-CR80" id="ref-link-section-d55432524e489">2007</a>).</p></div><div class="c-article-section__content"><p>Here, we will ponder mostly upon the first issue, while only touching on the second one. But before the answer is proposed, we must dwell a little into the physical and chemical properties of noble gases. As well as into some recent quantum mechanical calculations of noble gas containing molecules.</p></div><div class="c-article-section__content"><p>“Nobility” of certain elements has fascinated humans for millennia, gold serving as a base of monetary systems until the early XX century, but preserving its status as a reference measure of wealth to this day. The term “<i>noble gas</i>” has been coined at the end of the XIX century by Erdmann (cf. Renouf <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1901" title="Renouf, E.: Noble gases. Science 13(320), 268–270 (1901)" href="/article/10.1007/s10698-017-9302-7#ref-CR74" id="ref-link-section-d55432524e502">1901</a>) to describe the chemically inert gaseous elements known at that time (helium was discovered in 1868, argon in 1895, neon, krypton, and xenon in 1898, while radon in 1900) for which initially there was no room in the Mendeleyev’s Chart. For nearly one century since the discovery of helium chemists attempted to turn noble gases into chemical compounds, but they all failed, albeit some came very close. It was in the outburst of genius that Bartlett decided to react xenon with a small sample of PtF<sub>6</sub> which resulted in the isolation of the first noble gas compound (Bartlett <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1962" title="Bartlett, N.: Xenon hexafluoroplatinate (V) Xe+[PtF6]−. Proc. Chem. Soc. Lond. Chem. Soc. 6, 218 (1962)" href="/article/10.1007/s10698-017-9302-7#ref-CR3" id="ref-link-section-d55432524e507">1962</a>), what proved to be a mixture of several distinct compounds (Bartlett et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1976" title="Bartlett, N., Žemva, B., Graham, L.: Redox reactions in the XeF2/platinum fluoride and XeF2/palladium fluoride systems and the conversion of XeF2 to XeF4 and Xe. J. Fluor. Chem. 7(1–3), 301–320 (1976)" href="/article/10.1007/s10698-017-9302-7#ref-CR4" id="ref-link-section-d55432524e510">1976</a>), as it was finally confirmed only half a century from the initial discovery (Graham et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2000" title="Graham, L., Graudejus, O., Jha, N.K., Bartlett, N.: Concerning the nature of XePtF6. Coord. Chem. Rev. 197(1), 321–334 (2000)" href="/article/10.1007/s10698-017-9302-7#ref-CR31" id="ref-link-section-d55432524e514">2000</a>; Craciun et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2010" title="Craciun, R., Picone, D., Long, R.T., Li, S., Dixon, D.A., Peterson, K.A., Christe, K.O.: Third row transition metal hexafluorides, extraordinary oxidizers, and Lewis acids: electron affinities, fluoride affinities, and heats of formation of WF6, ReF6, OsF6, IrF6, PtF6, and AuF6. Inorg. Chem. 49(3), 1056–1070 (2010)" href="/article/10.1007/s10698-017-9302-7#ref-CR16" id="ref-link-section-d55432524e517">2010</a>; Seppelt <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2015" title="Seppelt, K.: Molecular hexafluorides. Chem. Rev. 115(2), 1296–1306 (2015)" href="/article/10.1007/s10698-017-9302-7#ref-CR83" id="ref-link-section-d55432524e520">2015</a>). The noble gas chemistry—particularly that of xenon and krypton, and including organoxenon chemistry (Naumann and Tyrra <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1989" title="Naumann, D., Tyrra, W.: The first compound with a stable xenon-carbon bond: 19F- and 129Xe-n.m.r. spectroscopic evidence for pentafluorophenylxenon(II) fluoroborates. J. Chem. Soc. Chem. Commun. 1, 47–50 (1989)" href="/article/10.1007/s10698-017-9302-7#ref-CR68" id="ref-link-section-d55432524e523">1989</a>; Frohn and Jakobs <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1989" title="Frohn, H.J., Jakobs, S.: The pentafluorophenylxenon(II) cation: [C6F5Xe]+; the first stable system with a xenon–carbon bond. J. Chem. Soc. Chem. Commun. 10, 625–627 (1989)" href="/article/10.1007/s10698-017-9302-7#ref-CR26" id="ref-link-section-d55432524e526">1989</a>)—has flourished since 1962 (Christe and Wilson <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1982" title="Christe, K.O., Wilson, W.W.: Perfluorammonium and alkali-metal salts of the heptafluoroxenon(VI) and octafluoroxenon(VI) anions. Inorg. Chem. 21(12), 4113–4117 (1982)" href="/article/10.1007/s10698-017-9302-7#ref-CR13" id="ref-link-section-d55432524e529">1982</a>; Christe et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1991" title="Christe, K.O., Curtis, E.C., Dixon, D.A., Mercier, H.P., Sanders, J.C.P., Schrobilgen, G.J.: The pentafluoroxenate(IV) anion, XeF5
 −: the first example of a pentagonal planar AX5 species. J. Am. Chem. Soc. 113(9), 3351–3361 (1991)" href="/article/10.1007/s10698-017-9302-7#ref-CR14" id="ref-link-section-d55432524e533">1991</a>; Dixon et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2007" title="Dixon, D.A., Wang, T.H., Grant, D.J., Peterson, K.A., Christe, K.O., Schrobilgen, G.J.: Heats of formation of krypton fluorides and stability predictions for KrF4 and KrF6 from high level electronic structure calculations. Inorg. Chem. 46(23), 10016–10021 (2007)" href="/article/10.1007/s10698-017-9302-7#ref-CR19" id="ref-link-section-d55432524e536">2007</a>), and even argon has proved to form a stable chemical compound, HArF, at sufficiently low temperatures (Khriachtchev et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2000" title="Khriachtchev, L., Pettersson, M., Runeberg, N., Lundell, J., Räsänen, M.: A stable argon compound. Nature 406, 874–876 (2000)" href="/article/10.1007/s10698-017-9302-7#ref-CR47" id="ref-link-section-d55432524e539">2000</a>)—it remains the only isolated chemical compound of argon. Consequently, with over half a thousand of currently known compounds of noble gases, their chemistry has been extensively reviewed during the last three decades (Laszlo and Schrobilgen <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1988" title="Laszlo, P., Schrobilgen, G.J.: One or several pioneers? The discovery of noble-gas compounds. Angew. Chem. Int. Ed. Engl. 27(4), 479–489 (1988)" href="/article/10.1007/s10698-017-9302-7#ref-CR52" id="ref-link-section-d55432524e542">1988</a>; Lehmann et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2002" title="Lehmann, J.F., Mercier, H.P.A., Schrobilgen, G.J.: The chemistry of krypton. Coord. Chem. Rev. 233–234, 1–39 (2002)" href="/article/10.1007/s10698-017-9302-7#ref-CR54" id="ref-link-section-d55432524e545">2002</a>; Schrobilgen and Moran <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2003" title="Schrobilgen, G.J., Moran, M.D.: Noble-gas compounds. In: Seidel, A., Bickford, M. (eds.) Kirk-Othmer Encyclopedia of Chemical Technology, vol. 16. Wiley, London (2003)" href="/article/10.1007/s10698-017-9302-7#ref-CR85" id="ref-link-section-d55432524e548">2003</a>; Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2007" title="Grochala, W.: Atypical compounds of gases, which have been called ‘noble’. Chem. Soc. Rev. 36(10), 1632–1655 (2007)" href="/article/10.1007/s10698-017-9302-7#ref-CR33" id="ref-link-section-d55432524e552">2007</a>; Grochala et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2011" title="Grochala, W., Khriachtchev, L., Räsänen, M.: Noble gas chemistry. In: Khriachtchev, L. (ed.) Physics and Chemistry at Low Temperatures, pp. 421–448. Pan Stanford Publishing, Cape Town (2011)" href="/article/10.1007/s10698-017-9302-7#ref-CR36" id="ref-link-section-d55432524e555">2011</a>; Brock et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2013" title="Brock, D. S., Schrobilgen, G. J., Žemva, B.: Noble-gas chemistry. In: Reedijk, J., Poeppelmeier, K. (eds.) Comprehensive Inorganic Chemistry II (Second Edition): From Elements to Applications, vol. 1, pp. 755–822 (2013). 
 http://www.sciencedirect.com/science/referenceworks/9780080965291
 
 
 " href="/article/10.1007/s10698-017-9302-7#ref-CR11" id="ref-link-section-d55432524e558">2013</a>; Hope <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2013" title="Hope, E.G.: Coordination chemistry of the noble gases and noble gas fluorides. Coord. Chem. Rev. 257(5–6), 902–909 (2013)" href="/article/10.1007/s10698-017-9302-7#ref-CR42" id="ref-link-section-d55432524e561">2013</a>; Haner and Schrobilgen <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2015" title="Haner, J., Schrobilgen, G.J.: The chemistry of xenon(IV). Chem. Rev. 115(2), 1255–1295 (2015)" href="/article/10.1007/s10698-017-9302-7#ref-CR40" id="ref-link-section-d55432524e564">2015</a>). Moreover, the experimental and theoretical chemistry and physics of noble gas compounds at high pressure started to flourish (Kim et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2010" title="Kim, M., Debessai, M., Yoo, C.-S.: Two- and three-dimensional extended solids and metallization of compressed XeF2. Nat. Chem. 2(9), 784–788 (2010)" href="/article/10.1007/s10698-017-9302-7#ref-CR48" id="ref-link-section-d55432524e567">2010</a>; Kurzydłowski et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2011" title="Kurzydłowski, D., Zaleski-Ejgierd, P., Grochala, W., Hoffmann, R.: Freezing in resonance structures for better packing: XeF2 becomes (XeF+)(F−) at large compression. Inorg. Chem. 50(8), 3832–3840 (2011)" href="/article/10.1007/s10698-017-9302-7#ref-CR50" id="ref-link-section-d55432524e571">2011</a>; Dong et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2017" title="Dong, X., Oganov, A.R., Goncharov, A.F., Stavrou, E., Lobanov, S., Saleh, G., Qian, G.-R., Zhu, Q., Gatti, C., Deringer, V.L., Dronskowski, R., Zhou, X.-F., Prakapenka, V., Konôpková, Z., Popov, I.A., Boldyrev, A.I., Wang, H.-T.: Stable compound of helium and sodium at high pressure. Nat. Chem. 9, 440–445 (2017)" href="/article/10.1007/s10698-017-9302-7#ref-CR20" id="ref-link-section-d55432524e574">2017</a>; Zhu et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2013" title="Zhu, Q., Jung, D.Y., Oganov, A.R., Glass, C.W., Gatti, C., Lyakhov, A.O.: Stability of xenon oxides at high pressures. Nat. Chem. 5(1), 61–65 (2013)" href="/article/10.1007/s10698-017-9302-7#ref-CR100" id="ref-link-section-d55432524e577">2013</a>, <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2014" title="Zhu, L., Liu, H., Pickard, C.J., Zou, G., Ma, Y.: Reactions of xenon with iron and nickel are predicted in the Earth’s inner core. Nat. Chem. 6(7), 644–648 (2014)" href="/article/10.1007/s10698-017-9302-7#ref-CR101" id="ref-link-section-d55432524e580">2014</a>; Hermann and Schwerdtfeger <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2014" title="Hermann, A., Schwerdtfeger, P.: Xenon suboxides stable under pressure. J. Phys. Chem. Lett. 5(24), 4336–4342 (2014)" href="/article/10.1007/s10698-017-9302-7#ref-CR41" id="ref-link-section-d55432524e583">2014</a>; Li et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2015" title="Li, X., Hermann, A., Peng, F., Lv, J., Wang, Y., Wang, H., Ma, Y.: Stable lithium argon compounds under high pressure. Sci. Rep. 5, 16675 (2015)" href="/article/10.1007/s10698-017-9302-7#ref-CR59" id="ref-link-section-d55432524e586">2015</a>; Dewaele et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2016" title="Dewaele, A., Worth, N., Pickard, C.J., Needs, R.J., Pascarelli, S., Mathon, O., Mezouar, M., Irifune, T.: Synthesis and stability of xenon oxides Xe2O5 and Xe3O2 under pressure. Nat. Chem. 8(8), 784–790 (2016)" href="/article/10.1007/s10698-017-9302-7#ref-CR18" id="ref-link-section-d55432524e590">2016</a>; Kurzydłowski and Zaleski-Ejgierd <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2016" title="Kurzydłowski, D., Zaleski-Ejgierd, P.: High-pressure stabilization of argon fluorides. Phys. Chem. Chem. Phys. 18(4), 2309–2313 (2016)" href="/article/10.1007/s10698-017-9302-7#ref-CR51" id="ref-link-section-d55432524e593">2016</a>), following the preliminary exploration a decade ago (Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2007" title="Grochala, W.: Atypical compounds of gases, which have been called ‘noble’. Chem. Soc. Rev. 36(10), 1632–1655 (2007)" href="/article/10.1007/s10698-017-9302-7#ref-CR33" id="ref-link-section-d55432524e596">2007</a>). One particularly interesting case is that of Na<sub>2</sub>He at very high pressures, which is called “stable” and “compound” by the authors (Dong et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2017" title="Dong, X., Oganov, A.R., Goncharov, A.F., Stavrou, E., Lobanov, S., Saleh, G., Qian, G.-R., Zhu, Q., Gatti, C., Deringer, V.L., Dronskowski, R., Zhou, X.-F., Prakapenka, V., Konôpková, Z., Popov, I.A., Boldyrev, A.I., Wang, H.-T.: Stable compound of helium and sodium at high pressure. Nat. Chem. 9, 440–445 (2017)" href="/article/10.1007/s10698-017-9302-7#ref-CR20" id="ref-link-section-d55432524e601">2017</a>), despite the fact that (1) high pressure is necessary to keep this species intact, and that (2) diverse bonding analyses point out to the lack of chemical bonding in this system. Peculiar Na<sub>2</sub>He calls for making our definitions of “compound” more precise (more on that anon in the last section).</p></div><div class="c-article-section__content"><p>Despite these impressive developments, neon and helium have <i>not</i> been forced to form genuine chemical bonds in <i>neutral entities</i> to this day. The status of the ingenious but fruitless efforts as of 1990 has been summarized in the insightful review (Frenking et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1990" title="Frenking, G., Koch, W., Reichel, F., Cremer, D.: Light noble-gas chemistry - structures, stabilities, and bonding of helium, neon and argon compounds. J. Am. Chem. Soc. 112(11), 4240–4256 (1990)" href="/article/10.1007/s10698-017-9302-7#ref-CR200" id="ref-link-section-d55432524e615">1990</a>). It is important to realize here that the genuine challenge in formation of noble gas species is connected with <i>electrically neutral systems</i>. This issue is similar in some aspects to the following one: what is the largest oxidation state which may be achieved for a given element? While this question is certainly very important, it should be specified that only <i>electrically neutral</i> isolable entities constitute real challenge in this matter; take uranium: it is not a major problem to generate U<sup>92+</sup> cations by physical means. However, it is a paramount obstacle to go beyond the formal oxidation state of U<sup>6+</sup> in neutral compounds of this element using chemical means. By a similar token, it is very easy to generate chemical bonds to helium, or to neon, letting alone argon and heavier noble gases—but one must use naked cations to bind them. To give an example: HAr<sup>+</sup> is an extremely common cationic species in gas spectrometry, which inevitably appears in every experiment conducted in the flow of “inert” argon gas. Similarly, HHe<sup>+</sup>—isoelectronic to H<sub>2</sub>—is very strongly bound, with the perfectly normal two-electron sigma bond, and the bond dissociation energy approaching 2 eV (as it has been calculated already in the early days of quantum mechanics over a century ago). HHe<sup>+</sup> is by no means elusive—it has been first observed in 1925. Indeed, a multitude of <i>helides</i>, i.e. MHe<span class="c-stack"> <sup>m+</sup><sub>n</sub> </span> cations, should be easy to prepare, as well, as they are usually very stable with respect to dissociation (Frenking et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1990" title="Frenking, G., Koch, W., Reichel, F., Cremer, D.: Light noble-gas chemistry - structures, stabilities, and bonding of helium, neon and argon compounds. J. Am. Chem. Soc. 112(11), 4240–4256 (1990)" href="/article/10.1007/s10698-017-9302-7#ref-CR200" id="ref-link-section-d55432524e648">1990</a>; Wilson et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2002" title="Wilson, D.J.D., Marsden, C.J., von Nagy-Felsobuki, E.I.: Ab initio structures and stabilities of doubly charged diatomic metal helides for the first row transition metals. J. Phys. Chem. A 106(32), 7348–7354 (2002)" href="/article/10.1007/s10698-017-9302-7#ref-CR98" id="ref-link-section-d55432524e651">2002</a>). Obviously, analogous cationic species containing neon or argon are even more facile to manufacture than those of helium, since Lewis basicity (measured by proton affinity) of light noble gas atoms increases in the order: He (1.84 eV) < Ne (2.06 eV) ≪ Ar (3.83 eV). Consequently, there is a vast literature on theoretical predictions of novel light noble gas-containing cations (Borocci et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2010" title="Borocci, S., Bronzolino, N., Giordani, M., Grandinetti, F.: Cationic noble gas hydrides: a theoretical investigation of dinuclear HNgFNgH+ (Ng = He − Xe). J. Phys. Chem. A 114(27), 7382–7390 (2010)" href="/article/10.1007/s10698-017-9302-7#ref-CR10" id="ref-link-section-d55432524e654">2010</a>; Rzepa <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2010" title="Rzepa, H.: The rational design of helium bonds. Nat. Chem. 2(5), 390–393 (2010)" href="/article/10.1007/s10698-017-9302-7#ref-CR76" id="ref-link-section-d55432524e657">2010</a>; Pan et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2016" title="Pan, S., Moreno, D., Ghosh, S., Chattaraj, P.K., Merino, G.: Structure and stability of noble gas bound EX3
 + compounds (E = C, Ge, Sn, Pb; X = H, F, Cl, Br). J. Comput. Chem. 37(2), 226–236 (2016)" href="/article/10.1007/s10698-017-9302-7#ref-CR70" id="ref-link-section-d55432524e661">2016</a>; these efforts were reviewed: Lewars <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2008" title="Lewars, E.G.: Modeling Marvels: Computational Anticipation of Novel Molecules, Chapter 5. Springer, Berlin (2008)" href="/article/10.1007/s10698-017-9302-7#ref-CR55" id="ref-link-section-d55432524e664">2008</a>) and experimental reports, as well (Cunje et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2001" title="Cunje, A., Baranov, V.I., Ling, Y., Hopkinson, A.C., Bohme, D.K.: Bonding of rare-gas atoms to Si in reactions of rare gases with SiF3
 +. J. Phys. Chem. A 105(49), 11073–11079 (2001)" href="/article/10.1007/s10698-017-9302-7#ref-CR17" id="ref-link-section-d55432524e667">2001</a>; Roithová and Schröder <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009" title="Roithová, J., Schröder, D.: Silicon compounds of Neon and Argon. Angew. Chem. Int. Ed. 48(46), 8788–8790 (2009)" href="/article/10.1007/s10698-017-9302-7#ref-CR75" id="ref-link-section-d55432524e670">2009</a>; Lockyear et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2010" title="Lockyear, J.F., Douglas, K., Price, S.D., Karwowska, M., Fijałkowski, K.J., Grochala, W., Remeš, M., Roithová, J., Schröder, D.: Generation of the ArCF2
 2+ dication. J. Phys. Chem. Lett. 1(1), 358–362 (2010)" href="/article/10.1007/s10698-017-9302-7#ref-CR63" id="ref-link-section-d55432524e673">2010</a>), to mention just a few examples. However, the neutral (solid state) analogues of helides (stabilized by counteranions) do not exist albeit their first xenon analogues were successfully prepared (Seppelt and Seidel <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2000" title="Seppelt, K., Seidel, S.: Xenon as a complex ligand: the tetraxenono gold(II) cation in AuXe4
 2+(Sb2F11
 −)2. Science 290(5489), 117–118 (2000)" href="/article/10.1007/s10698-017-9302-7#ref-CR87" id="ref-link-section-d55432524e676">2000</a>; Hwang et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2003" title="Hwang, I.C., Seidel, S., Seppelt, K.: Gold(I) and Mercury(II) Xenon Complexes. Angew. Chem. Int. Ed. 42(36), 4392–4395 (2003)" href="/article/10.1007/s10698-017-9302-7#ref-CR43" id="ref-link-section-d55432524e680">2003</a>).</p></div><div class="c-article-section__content"><p>Noticing the usual stability order of light noble gas species: cationic ≫ anionic > neutral (Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009a" title="Grochala, W.: On chemical bonding between helium and oxygen. Pol. J. Chem. 83(1), 87–122 (2009a)" href="/article/10.1007/s10698-017-9302-7#ref-CR34" id="ref-link-section-d55432524e686">2009a</a>), it is not surprising that also some anions were predicted to constitute local minima on the potential energy surface (Liu et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2012" title="Liu, G., Zhang, Y., Bai, X., He, F., Zhang, X., Wang, Z., Zhang, W.: Theoretical investigation of the noble gas molecular anions XAuNgX− and HAuNgX− (X = F, Cl, Br; Ng = Xe, Kr, Ar). Struct. Chem. 23(6), 1693–1710 (2012)" href="/article/10.1007/s10698-017-9302-7#ref-CR61" id="ref-link-section-d55432524e689">2012</a>). The most remarkable cases are those of FNgO<sup>−</sup> (Li et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2005" title="Li, T.-H., Mou, C.-H., Chen, H.-R., Hu, W.-P.: Theoretical prediction of noble gas containing anions FNgO− (Ng = He, Ar, and Kr). J. Am. Chem. Soc. 127(25), 9241–9245 (2005)" href="/article/10.1007/s10698-017-9302-7#ref-CR58" id="ref-link-section-d55432524e694">2005</a>) and of related F<sup>−</sup>(NgO)<sub>n</sub> (Liu et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2007" title="Liu, Y.-L., Chang, Y.-H., Li, T.-H., Chen, H.-R., Hu, W.-P.: Theoretical study on the noble-gas anions F−(NgO)n (Ng = He, Ar, and Kr). Chem. Phys. Lett. 439(1–3), 14–17 (2007)" href="/article/10.1007/s10698-017-9302-7#ref-CR62" id="ref-link-section-d55432524e702">2007</a>) where Ng = He, Ar, and Kr. These species are bound on the singlet potential energy surface but the ground state of the system corresponds to triplet, F<sup>−</sup> + Ng + <sup>3</sup>O. An independent suggestion of metastable FNgO<sup>−</sup> anions came later from theorizing a possible oxidation of NG atoms by powerful O<sub>n</sub>F<sub>m</sub> oxidizers, while taking into account that high oxidation state of chemical elements is easier achieved in anionic than in neutral species (Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009a" title="Grochala, W.: On chemical bonding between helium and oxygen. Pol. J. Chem. 83(1), 87–122 (2009a)" href="/article/10.1007/s10698-017-9302-7#ref-CR34" id="ref-link-section-d55432524e716">2009a</a>). Thus, FNgO<sup>−</sup> may be viewed as a product of insertion of He into the O–F bond of the OF<sup>−</sup> anion, itself a derivative of a metastable HOF acid.</p></div><div class="c-article-section__content"><p>Having understood that this is not difficult for noble gas atoms to form chemical bonds per se, but this is quite challenging to achieve bonding in <i>neutral moieties</i> (i.e. <i>chemical compounds</i>), we turn to the latter. Unfortunately, most of such connections are bound by weak forces and they may be classified as van der Waals complexes (Zou et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2013" title="Zou, W., Nori-Shargh, D., Boggs, J.E.: On the covalent character of rare gas bonding interactions: a new kind of weak interaction. J. Phys. Chem. A 117(1), 207–212 (2013)" href="/article/10.1007/s10698-017-9302-7#ref-CR103" id="ref-link-section-d55432524e732">2013</a>; Cappelletti et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2015" title="Cappelletti, D., Bartocci, A., Grandinetti, F., Falcinelli, S., Belpassi, L., Tarantelli, F., Pirani, F.: Experimental evidence of chemical components in the bonding of helium and neon with neutral molecules. Chem. Eur. J. 21(16), 6234–6240 (2015)" href="/article/10.1007/s10698-017-9302-7#ref-CR12" id="ref-link-section-d55432524e735">2015</a>). This is e.g. the case of adducts of Group 11 halide molecules with light noble gases—the binding energies do not surpass 0.25 eV (for ArAgF, Evans and Gerry <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2000" title="Evans, C.J., Gerry, M.C.L.: The microwave spectra and structures of Ar–AgX (X = F, Cl, Br). J. Chem. Phys. 112(3), 1321–1329 (2000)" href="/article/10.1007/s10698-017-9302-7#ref-CR21" id="ref-link-section-d55432524e738">2000</a>; Lovallo and Kłobukowski <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2003" title="Lovallo, C.C., Kłobukowski, M.: Transition metal-noble gas bonding: the next frontier. Chem. Phys. Lett. 368(5), 589–593 (2003)" href="/article/10.1007/s10698-017-9302-7#ref-CR64" id="ref-link-section-d55432524e742">2003</a>; Belpassi et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2008" title="Belpassi, L., Infante, I., Tarantelli, F., Visscher, L.: The chemical bond between Au(I) and the noble gases. Comparative study of NgAuF and NgAu+ (Ng = Ar, Kr, Xe) by density functional and coupled cluster methods. J. Am. Chem. Soc. 130(3), 1048–1060 (2008)" href="/article/10.1007/s10698-017-9302-7#ref-CR6" id="ref-link-section-d55432524e745">2008</a>), and they are calculated to be even smaller for Ne and He (Zou et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009" title="Zou, L., Liu, Y., Boggs, J.E.: Theoretical study of RgMF (Rg = He, Ne; M = Cu, Ag, Au): bonded structures of helium. Chem. Phys. Lett. 482(4–6), 207–210 (2009)" href="/article/10.1007/s10698-017-9302-7#ref-CR102" id="ref-link-section-d55432524e748">2009</a>). Nevertheless, the adduct of Ne with AuF has been observed experimentally (Wang et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2013" title="Wang, X., Andrews, L., Brosi, F., Riedel, S.: Matrix infrared spectroscopy and quantum-chemical calculations for the coinage-metal fluorides: comparisons of Ar–AuF, Ne–AuF, and molecules MF2 and MF3. Chem. Eur. J. 19(4), 1397–1409 (2013)" href="/article/10.1007/s10698-017-9302-7#ref-CR96" id="ref-link-section-d55432524e751">2013</a>) and its dissociation energy has been estimated to be smaller than 0.1 eV. Regretfully, the infra-red absorption bands corresponding to Ne···Au stretching and Ne···Au···F bending modes have not been observed.</p></div><div class="c-article-section__content"><p>These were Frenking and colleagues (Koch et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1986" title="Koch, W., Collins, J.R., Frenking, G.: Are there neutral helium compounds which are stable in their ground state? A theoretical investigation of HeBCH and HeBeO. Chem. Phys. Lett. 132(3), 330–333 (1986)" href="/article/10.1007/s10698-017-9302-7#ref-CR49" id="ref-link-section-d55432524e757">1986</a>; Frenking et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1988" title="Frenking, G., Koch, W., Gauss, J., Cremer, D.: Stabilities and nature of the attractive interactions in HeBeO, NeBeO, and ArBeO and a comparison with analogs NGLiF, NGBN, and NGLiH (NG = He, Ar). A theoretical investigation. J. Am. Chem. Soc. 110(24), 8007–8016 (1988)" href="/article/10.1007/s10698-017-9302-7#ref-CR23" id="ref-link-section-d55432524e760">1988</a>) who were the first to theoretically study molecules bearing light noble gas atoms attached to coordinatively unsaturated metal centers, notably Be<sup>2+</sup>, in neutral molecules. An analogous matrix species containing argon, ArBeO, was prepared (Thompson and Andrews <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1994" title="Thompson, C.A., Andrews, L.: Noble-gas complexes with BeO—infrared-spectra of NG-BeO (NG = Ar, Kr, Xe). J. Am. Chem. Soc. 116(1), 423–424 (1994)" href="/article/10.1007/s10698-017-9302-7#ref-CR93" id="ref-link-section-d55432524e765">1994</a>) following the above-mentioned theoretical proposal that the strong electric field outside the small, highly charged Be<sup>2+</sup> cation of BeO could bind rare-gas atoms through their electric dipole polarizability. But the calculated Ar–Be bond energy is only 0.3 eV, and the bond can only be considered as anomalously strongly bound van der Waals complex rather than covalently bound moiety. This is also the case of the related NeBeS adduct which exhibits an even smaller value of the bonding energy (Wang and Wang <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2013" title="Wang, Q., Wang, X.: Infrared spectra of NgBeS (Ng = Ne, Ar, Kr, Xe) and BeS2 in noble-gas matrices. J. Phys. Chem. A 117(7), 1508–1513 (2013)" href="/article/10.1007/s10698-017-9302-7#ref-CR97" id="ref-link-section-d55432524e771">2013</a>). No helium adducts of this kind were ever prepared, albeit they have been theorized. Similarly, isoelectronic adducts of the type RNBeNG (where R is an electronegative substituent) were studied theoretically (Antoniotti et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2003" title="Antoniotti, P., Bronzolino, N., Grandinetti, F.: Stable compounds of the lightest noble gases: a computational investigation of RNBeNg (Ng = He, Ne, Ar). J. Phys. Chem. A 107(16), 2974–2980 (2003)" href="/article/10.1007/s10698-017-9302-7#ref-CR1" id="ref-link-section-d55432524e774">2003</a>), with the conclusion that they might constitute viable experimental targets. Not surprisingly, for all complexes which are weakly bound via polarization forces, stability of helium adducts is somewhat smaller than that of the respective neon ones (helium has just two electrons, while neon has ten).</p></div><div class="c-article-section__content"><p>The neutral compounds of helium and neon bearing strong covalent bonds to noble gas atom were considered nearly half a century ago (Liebman and Allen <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1970" title="Liebman, J.F., Allen, L.C.: A salt chemistry of light noble gas compounds. J. Am. Chem. Soc. 92(12), 3539–3543 (1970)" href="/article/10.1007/s10698-017-9302-7#ref-CR60" id="ref-link-section-d55432524e780">1970</a>). These authors have noticed that the <sup>1</sup>Σ singlet states of NGF<sup>+</sup> (NG = He, Ne) cations exhibit short equilibrium bond lengths (1.33 Å for He; 1.65 Å for Ne, indicative of covalent bonding) and they are bound by over 1.2 eV (albeit helium species slightly more than the neon one!); these authors have speculated that salts of these cations might be prepared. These predictions were never confirmed in experiment. One major difficulty in obtaining such salts sits in immense oxidizing power of NGF<sup>+</sup> cations, and another in the fact that their ground state corresponds to a dissociative triplet state, and it is placed over 2 eV below the above-mentioned singlet. Thus—if preparable—these salts would likely be thermally unstable or even explosive. Following a similar line of reasoning it was pointed out that the ArH<sup>+</sup> salts in the solid state (letting alone the NeH<sup>+</sup> and HeH<sup>+</sup> ones!) are unlikely to be prepared since we currently do not have a Lewis acid powerful enough to withdraw F<sup>−</sup> anion from the neutral HArF molecule (Christe <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2001" title="Christe, K.O.: A renaissance in noble gas chemistry. Angew. Chem. Int. Ed. Engl. 40(8), 1419–1421 (2001)" href="/article/10.1007/s10698-017-9302-7#ref-CR15" id="ref-link-section-d55432524e798">2001</a>). In other words, the salts bearing NGF<sup>+</sup> or NGH<sup>+</sup> cations (NG = Ar, Ne, He) would, by necessity, be thermodynamically unstable albeit possibly metastable (Frenking et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1989" title="Frenking, G., Koch, W., Deakyne, C.A., Liebman, J.F., Bartlett, N.: The ArF+ cation. Is it stable enough to be isolated in a salt? J. Am. Chem. Soc. 111(1), 31–33 (1989)" href="/article/10.1007/s10698-017-9302-7#ref-CR24" id="ref-link-section-d55432524e806">1989</a>). For example, ArFSbF<sub>6</sub> was estimated to be unstable by over 1 eV with respect to Ar, F<sub>2</sub> and SbF<sub>5</sub>. It is completely unclear at this moment what reaction pathways could be used to generate such metastable species, since even more unstable precursors should possibly be used for a facile (downhill) reaction. For example, superhalogens were suggested as one possible substrate of this reaction (Samanta <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2014" title="Samanta, D.: Prediction of superhalogen-stabilized noble gas compounds. J. Phys. Chem. Lett. 5(18), 3151–3156 (2014)" href="/article/10.1007/s10698-017-9302-7#ref-CR77" id="ref-link-section-d55432524e815">2014</a>) but this strategy has not yet been tested in theoretical calculations for the two lightest noble gases.</p></div><div class="c-article-section__content"><p>With HArF successfully isolated, HNeF and HHeF became obvious targets. The first theoretical study has indicated that HHeF is a local minimum at the potential energy surface, while its neon analogue is not (at the CCSD level of theory) (Wong <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2000" title="Wong, M.W.: Prediction of a metastable helium compound: HHeF. J. Am. Chem. Soc. 122(26), 6289–6290 (2000)" href="/article/10.1007/s10698-017-9302-7#ref-CR99" id="ref-link-section-d55432524e822">2000</a>). However, the ZPE-corrrected energy barrier for the highly exoenergetic dissociation (by nearly 7 eV!) to HF and He amounts to 25.3 kJ mol<sup>−1</sup> which may not be sufficient for isolating of this molecule (Wong <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2000" title="Wong, M.W.: Prediction of a metastable helium compound: HHeF. J. Am. Chem. Soc. 122(26), 6289–6290 (2000)" href="/article/10.1007/s10698-017-9302-7#ref-CR99" id="ref-link-section-d55432524e827">2000</a>). Subsequent studies using multireference methods have showed that the barrier is even smaller than initially thought, and the predicted lifetime of HHeF is only 157 fs (Takayanagi and Wada <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2002" title="Takayanagi, T., Wada, A.: Theoretical prediction of the lifetime of the metastable helium compound: HHeF. Chem. Phys. Lett. 352(1–2), 91–98 (2002)" href="/article/10.1007/s10698-017-9302-7#ref-CR201" id="ref-link-section-d55432524e830">2002</a>). It was also suggested that HHeF cannot be sufficiently well stabilized by complexation (Giordani et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2010" title="Giordani, M., Antoniotti, P., Grandinetti, F.: Stabilization of HHeF by complexation: is it a really viable strategy? Chem. Eur. J. 16(21), 6257–6264 (2010)" href="/article/10.1007/s10698-017-9302-7#ref-CR29" id="ref-link-section-d55432524e833">2010</a>). Some authors considered placing (or in situ generating of) HHeF molecules in the helium matrix and applying high pressure (Bihary et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2002" title="Bihary, Z., Chaban, G.M., Gerber, R.B.: Stability of a chemically bound helium compound in high-pressure solid helium. J. Chem. Phys. 117(11), 5105–5108 (2002)" href="/article/10.1007/s10698-017-9302-7#ref-CR8" id="ref-link-section-d55432524e837">2002</a>). Albeit the bonds to NG are stiffened at high pressure, this strategy has multiple problems, such as for example necessity to keep the HHeF molecules strictly isolated from one another. Moreover, subsequent calculations have showed that HHeF molecules are far from being thermodynamically stable even at huge pressure of 500 GPa (Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2014" title="Grochala, W.: Unpublished periodic DFT results (2014)" href="/article/10.1007/s10698-017-9302-7#ref-CR39" id="ref-link-section-d55432524e840">2014</a>). Last but not least, HNgCl molecules were also theoretically studied (McDowell <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2001" title="McDowell, S.A.C.: Are H–He–Cl and H–Ne–Cl metastable species? A computational study. Chem. Phys. Lett. 342(5–6), 631–635 (2001)" href="/article/10.1007/s10698-017-9302-7#ref-CR66" id="ref-link-section-d55432524e843">2001</a>); the CISD results suggest that, just like in the case of fluoride derivative, the stoichiometry containing neon does not correspond to a minimum at the potential energy surface, while the helium species is a genuine minimum. Both authors (Wong <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2000" title="Wong, M.W.: Prediction of a metastable helium compound: HHeF. J. Am. Chem. Soc. 122(26), 6289–6290 (2000)" href="/article/10.1007/s10698-017-9302-7#ref-CR99" id="ref-link-section-d55432524e846">2000</a>; McDowell <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2001" title="McDowell, S.A.C.: Are H–He–Cl and H–Ne–Cl metastable species? A computational study. Chem. Phys. Lett. 342(5–6), 631–635 (2001)" href="/article/10.1007/s10698-017-9302-7#ref-CR66" id="ref-link-section-d55432524e849">2001</a>) tend to assign the lack of stability of neon species to a weaker electrostatic attraction between H<sup>+</sup> and F<sup>−</sup> (or Cl<sup>−</sup>) due to a larger radius of neon than that of helium (and thus a larger anion–cation separation). The HNgX molecules described in this section fall into category of push–pull systems, with the predominant resonance structure of the type: [H<sup>+</sup>←Ng]···X<sup>−</sup>. In this way, NG atom with the stable doublet (He) or octet (Ne) electronic configuration avoids being pushed into a hypervalent bonding (for a critical discussion of a concept of hypervalence cf. Gillespie and Silvi <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2002" title="Gillespie, R.J., Silvi, B.: The octet rule and hypervalence: two misunderstood concepts. Coord. Chem. Rev. 233–234, 53–62 (2002)" href="/article/10.1007/s10698-017-9302-7#ref-CR28" id="ref-link-section-d55432524e863">2002</a>).</p></div><div class="c-article-section__content"><p>The last type of molecules containing covalently bound He, which have been theorized in the past, are the derivatives of helium monoxide, HeO, with small molecules which exhibit substantial dipole moment (Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009a" title="Grochala, W.: On chemical bonding between helium and oxygen. Pol. J. Chem. 83(1), 87–122 (2009a)" href="/article/10.1007/s10698-017-9302-7#ref-CR34" id="ref-link-section-d55432524e869">2009a</a>, <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2012" title="Grochala, W.: Metastable He–O bond inside a ferroelectric molecular cavity: (HeO)(LiF)2. Phys. Chem. Chem. Phys. 14, 14860–14868 (2012)" href="/article/10.1007/s10698-017-9302-7#ref-CR37" id="ref-link-section-d55432524e872">2012</a>). These include: (HeO)(MF) where M = Cs, NMe<sub>4</sub>, as well as (HeO)(LiF)<sub>2</sub>. The (HeO)(MF) systems may be viewed as derivatives of the previously discussed OHeF<sup>−</sup> anion (Li et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2005" title="Li, T.-H., Mou, C.-H., Chen, H.-R., Hu, W.-P.: Theoretical prediction of noble gas containing anions FNgO− (Ng = He, Ar, and Kr). J. Am. Chem. Soc. 127(25), 9241–9245 (2005)" href="/article/10.1007/s10698-017-9302-7#ref-CR58" id="ref-link-section-d55432524e882">2005</a>) with the large and soft cation, which does not destroy the integrity of the anionic species. The proposed synthetic pathway towards (HeO)(MF) systems relies on a photochemical reaction between He and MOF molecule, where the σ → σ* excitation of the O–F bond would permit the insertion of noble gas atom and formation of the metastable target species (Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009a" title="Grochala, W.: On chemical bonding between helium and oxygen. Pol. J. Chem. 83(1), 87–122 (2009a)" href="/article/10.1007/s10698-017-9302-7#ref-CR34" id="ref-link-section-d55432524e885">2009a</a>). This observation has led this author to postulate that neon is in fact the most noble of noble gases, and it should be the first member of the Group 18, with helium moved to the Group 2 of the Periodic Table (Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009a" title="Grochala, W.: On chemical bonding between helium and oxygen. Pol. J. Chem. 83(1), 87–122 (2009a)" href="/article/10.1007/s10698-017-9302-7#ref-CR34" id="ref-link-section-d55432524e888">2009a</a>, <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference b" title="Grochala, W.: Quo vadis noble gas chemistry? Talk at Universita de la Tuscia, Viterbo, Jun 9 (2009b)" href="/article/10.1007/s10698-017-9302-7#ref-CR35" id="ref-link-section-d55432524e891">b</a>, <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2013" title="Grochala, W.: Can elemental helium form chemical bonds in neutral molecules? Wissenschaftsforum Chemie 2013. Darmstadt, Germany (2013)" href="/article/10.1007/s10698-017-9302-7#ref-CR38" id="ref-link-section-d55432524e894">2013</a>).</p></div><div class="c-article-section__content"><p>On the other hand, metastable (HeO)(LiF)<sub>2</sub> is best described as HeO molecule embedded into a ferroelectric cavity composed of two parallel LiF dipoles (Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2012" title="Grochala, W.: Metastable He–O bond inside a ferroelectric molecular cavity: (HeO)(LiF)2. Phys. Chem. Chem. Phys. 14, 14860–14868 (2012)" href="/article/10.1007/s10698-017-9302-7#ref-CR37" id="ref-link-section-d55432524e902">2012</a>). This interesting minimum on the potential energy surface features a short covalent He–O bond at ~ 1.15 Å; the bond is slightly polarized with the electrons transferred <i>from helium to oxygen</i> (He<sup>δ+</sup>O<sup>δ−</sup>). This suggests that neutral helium atom is a lone pair donor towards an unusual Lewis acid: a singlet oxygen atom (He → <sup>1</sup>O). The (HeO)(LiF)<sub>2</sub> molecule is also different from other neutral species bearing helium by the fact that the noble gas atom has only one close neighbor and the <i>trans</i> position is free (this helps to avoid hypervalence at helium). Remarkably, the neon analogue does not correspond to a minimum (Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2012" title="Grochala, W.: Metastable He–O bond inside a ferroelectric molecular cavity: (HeO)(LiF)2. Phys. Chem. Chem. Phys. 14, 14860–14868 (2012)" href="/article/10.1007/s10698-017-9302-7#ref-CR37" id="ref-link-section-d55432524e920">2012</a>) but the heavier noble gases form the minima on the singlet potential energy surface (Szarek and Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2015" title="Szarek, P., Grochala, W.: Noble gas monoxides stabilized in dipolar cavity: a theoretical study. J. Phys. Chem. A 119(11), 2483–2489 (2015)" href="/article/10.1007/s10698-017-9302-7#ref-CR90" id="ref-link-section-d55432524e923">2015</a>). Moreover, there is a striking similarity between the molecular geometries of (HeO)(LiF)<sub>2</sub> and (BeO)(LiF)<sub>2</sub> (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig4">4</a>). Helium seems to show affinity to oxygen, just like beryllium does. This observation, again, led this author to reconsider the position of helium and neon in the Periodic Table (cf. parts S13–S15 of the electronic supplementary information; Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2012" title="Grochala, W.: Metastable He–O bond inside a ferroelectric molecular cavity: (HeO)(LiF)2. Phys. Chem. Chem. Phys. 14, 14860–14868 (2012)" href="/article/10.1007/s10698-017-9302-7#ref-CR37" id="ref-link-section-d55432524e934">2012</a>). If such He ~ Be analogy were pushed further, one might evaluate the ionic radius of He<sup>2+</sup> to be about 0.06 Å (the ionic radius of Be<sup>2+</sup> is quoted at 0.41 Å, while the bond length difference between Be–O and He–O bonds is computed to be about 0.35 Å, Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig4">4</a>). The value obtained is reasonably close to the expected value of ~ 0.0 Å.</p><div class="c-article-section__figure js-c-reading-companion-figures-item" data-test="figure" data-container-section="figure" id="figure-4" data-title="Fig. 4"><figure><figcaption><b id="Fig4" class="c-article-section__figure-caption" data-test="figure-caption-text">Fig. 4</b></figcaption><div class="c-article-section__figure-content"><div class="c-article-section__figure-item"><a class="c-article-section__figure-link" data-test="img-link" data-track="click" data-track-label="image" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/4" rel="nofollow"><picture><source type="image/webp" srcset="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig4_HTML.gif?as=webp"><img aria-describedby="Fig4" src="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig4_HTML.gif" alt="figure 4" loading="lazy"></picture></a></div><div class="c-article-section__figure-description" data-test="bottom-caption" id="figure-4-desc"><p>Comparison of the calculated molecular geometry of (HeO)(LiF)<sub>2</sub> and (BeO)(LiF)<sub>2</sub> (reproduced with permission from Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2012" title="Grochala, W.: Metastable He–O bond inside a ferroelectric molecular cavity: (HeO)(LiF)2. Phys. Chem. Chem. Phys. 14, 14860–14868 (2012)" href="/article/10.1007/s10698-017-9302-7#ref-CR37" id="ref-link-section-d55432524e959">2012</a>)</p></div></div><div class="u-text-right u-hide-print"><a class="c-article__pill-button" data-test="article-link" data-track="click" data-track-label="button" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/4" data-track-dest="link:Figure4 Full size image" aria-label="Full size image figure 4" rel="nofollow"><span>Full size image</span><svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-chevron-right-small"></use></svg></a></div></figure></div> </div><div class="c-article-section__content"><p>The striking relative inertness of neon—in cationic, anionic and neutral systems—has been noticed before by several authors independently (Frenking and Cremer <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1990" title="Frenking, G., Cremer, D.: The chemistry of the noble gas elements helium, neon, and argon—experimental facts and theoretical predictions. Struct. Bonding 73, 17 (1990)" href="/article/10.1007/s10698-017-9302-7#ref-CR25" id="ref-link-section-d55432524e974">1990</a>; Wong <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2000" title="Wong, M.W.: Prediction of a metastable helium compound: HHeF. J. Am. Chem. Soc. 122(26), 6289–6290 (2000)" href="/article/10.1007/s10698-017-9302-7#ref-CR99" id="ref-link-section-d55432524e977">2000</a>; Lundell et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2000" title="Lundell, J., Chaban, G.M., Gerber, R.B.: Combined ab initio and anharmonic vibrational spectroscopy calculations for rare gas containing fluorohydrides, HRgF. Chem. Phys. Lett. 331(2–4), 308–316 (2000)" href="/article/10.1007/s10698-017-9302-7#ref-CR65" id="ref-link-section-d55432524e980">2000</a>; McDowell <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2001" title="McDowell, S.A.C.: Are H–He–Cl and H–Ne–Cl metastable species? A computational study. Chem. Phys. Lett. 342(5–6), 631–635 (2001)" href="/article/10.1007/s10698-017-9302-7#ref-CR66" id="ref-link-section-d55432524e983">2001</a>; Li et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2005" title="Li, T.-H., Mou, C.-H., Chen, H.-R., Hu, W.-P.: Theoretical prediction of noble gas containing anions FNgO− (Ng = He, Ar, and Kr). J. Am. Chem. Soc. 127(25), 9241–9245 (2005)" href="/article/10.1007/s10698-017-9302-7#ref-CR58" id="ref-link-section-d55432524e986">2005</a>; Liu et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2007" title="Liu, Y.-L., Chang, Y.-H., Li, T.-H., Chen, H.-R., Hu, W.-P.: Theoretical study on the noble-gas anions F−(NgO)n (Ng = He, Ar, and Kr). Chem. Phys. Lett. 439(1–3), 14–17 (2007)" href="/article/10.1007/s10698-017-9302-7#ref-CR62" id="ref-link-section-d55432524e990">2007</a>; Borocci et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2008" title="Borocci, S., Bronzolino, N., Grandinetti, F.: Noble gas–sulfur anions: a theoretical investigation of FNgS − (Ng = He, Ar, Kr, Xe). Chem. Phys. Lett. 458(1–3), 48–53 (2008)" href="/article/10.1007/s10698-017-9302-7#ref-CR9" id="ref-link-section-d55432524e993">2008</a>). Notably, a hypothetical (F<sup>−</sup>···NeBN) anion remains the only metastable anionic species which contains chemically bound Ne atom—an analogous He species is predicted to be much more strongly bound (Antoniotti et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2007" title="Antoniotti, P., Borocci, S., Bronzolino, N., Cecchi, P., Grandinetti, F.: Noble gas anions: a theoretical investigation of FNgBN− (Ng = He–Xe). J. Phys. Chem. A 111(40), 10144–10151 (2007)" href="/article/10.1007/s10698-017-9302-7#ref-CR2" id="ref-link-section-d55432524e998">2007</a>). The inertness of neon has been traditionally assigned to the Pauli repulsion involving 2<i>p</i> shell—note: helium lacks p electrons, hence Pauli repulsion is greatly reduced. Interestingly, none of these authors has suggested that this implies that neon is the most inert noble gas. It was finally Grandinetti who admitted such possibility (Grandinetti <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2013" title="Grandinetti, F.: Neon behind the signs. Nat. Chem. 5(5), 438 (2013)" href="/article/10.1007/s10698-017-9302-7#ref-CR32" id="ref-link-section-d55432524e1004">2013</a>), he failed, however, to specifically cite all earlier proposers (Bent <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2006" title="Bent, H.: New ideas in chemistry from fresh energy for the periodic law. AuthorHouse, Bloomington (2006)" href="/article/10.1007/s10698-017-9302-7#ref-CR7" id="ref-link-section-d55432524e1008">2006</a>; Scerri <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2007" title="Scerri, E.R.: The Periodic Table: Its Story and Its Significance. Oxford University Press, Oxford (2007)" href="/article/10.1007/s10698-017-9302-7#ref-CR80" id="ref-link-section-d55432524e1011">2007</a>; Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009a" title="Grochala, W.: On chemical bonding between helium and oxygen. Pol. J. Chem. 83(1), 87–122 (2009a)" href="/article/10.1007/s10698-017-9302-7#ref-CR34" id="ref-link-section-d55432524e1014">2009a</a>, <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference b" title="Grochala, W.: Quo vadis noble gas chemistry? Talk at Universita de la Tuscia, Viterbo, Jun 9 (2009b)" href="/article/10.1007/s10698-017-9302-7#ref-CR35" id="ref-link-section-d55432524e1017">b</a>, <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2012" title="Grochala, W.: Metastable He–O bond inside a ferroelectric molecular cavity: (HeO)(LiF)2. Phys. Chem. Chem. Phys. 14, 14860–14868 (2012)" href="/article/10.1007/s10698-017-9302-7#ref-CR37" id="ref-link-section-d55432524e1020">2012</a>), which resulted in an exchange of correspondence between Roald Hoffmann, Felice Grandinetti and the journal editor (Pichon <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2013" title="Pichon, A.: A letter about ‘Neon behind the signs’. Nature Chemistry blog “The Sceptical Chymist” (2013). 
 http://blogs.nature.com/thescepticalchymist/2013/12/a-letter-about-neon-behind-the-signs.html
 
 
 " href="/article/10.1007/s10698-017-9302-7#ref-CR71" id="ref-link-section-d55432524e1023">2013</a>).</p></div><div class="c-article-section__content"><p>Let us reanalyze here different aspects of various placements of helium and neon in the Periodic Table (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig5">5</a>), as quantified by the first ionization potential and the first electron affinity of elements from Groups 1, 2, 17 and 18 (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig6">6</a>), issues of scientific priority aside. We have focused primarily on these two energy-related parameters of atoms, as they govern many physical and chemical properties of elements. To clearly observe the <i>trends of properties</i> we always normalize the absolute values to the value exhibited by the first (lightest) member of the series and we then draw the plots with respect to the period number of the Periodic Chart. Graphs on the left in Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig6">6</a> correspond to situation C) from Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig5">5</a>, those in the middle to B), and those on the right to the traditional variant A).</p><div class="c-article-section__figure js-c-reading-companion-figures-item" data-test="figure" data-container-section="figure" id="figure-5" data-title="Fig. 5"><figure><figcaption><b id="Fig5" class="c-article-section__figure-caption" data-test="figure-caption-text">Fig. 5</b></figcaption><div class="c-article-section__figure-content"><div class="c-article-section__figure-item"><a class="c-article-section__figure-link" data-test="img-link" data-track="click" data-track-label="image" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/5" rel="nofollow"><picture><source type="image/webp" srcset="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig5_HTML.gif?as=webp"><img aria-describedby="Fig5" src="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig5_HTML.gif" alt="figure 5" loading="lazy"></picture></a></div><div class="c-article-section__figure-description" data-test="bottom-caption" id="figure-5-desc"><p>Four possible positions of He in the Periodic Table of Chemical Elements: <b>a</b> classical version placing H in Group 1 and He in Group 18; <b>b</b> alternative version, which emphasizes similarity of H to halogens; Scerri’s proposal differs but preserves the placement of H, F, He and Ne (Scerri <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009" title="Scerri, E.R.: Periodic change. Chem. World 3, 46–49 (2009)" href="/article/10.1007/s10698-017-9302-7#ref-CR81" id="ref-link-section-d55432524e1061">2009</a>); <b>c</b> version placing He out of the noble gas group, close to H and simultaneously above Be (and not above Ne); <b>d</b> IUPAC-supported version placing H in a distinct group No. 0, while He stays in Group 18. The theoretical (computational) results described here support version (<b>c</b>) (reproduced with permission from Grochala <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009a" title="Grochala, W.: On chemical bonding between helium and oxygen. Pol. J. Chem. 83(1), 87–122 (2009a)" href="/article/10.1007/s10698-017-9302-7#ref-CR34" id="ref-link-section-d55432524e1074">2009a</a>)</p></div></div><div class="u-text-right u-hide-print"><a class="c-article__pill-button" data-test="article-link" data-track="click" data-track-label="button" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/5" data-track-dest="link:Figure5 Full size image" aria-label="Full size image figure 5" rel="nofollow"><span>Full size image</span><svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-chevron-right-small"></use></svg></a></div></figure></div> <div class="c-article-section__figure js-c-reading-companion-figures-item" data-test="figure" data-container-section="figure" id="figure-6" data-title="Fig. 6"><figure><figcaption><b id="Fig6" class="c-article-section__figure-caption" data-test="figure-caption-text">Fig. 6</b></figcaption><div class="c-article-section__figure-content"><div class="c-article-section__figure-item"><a class="c-article-section__figure-link" data-test="img-link" data-track="click" data-track-label="image" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/6" rel="nofollow"><picture><source type="image/webp" srcset="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig6_HTML.gif?as=webp"><img aria-describedby="Fig6" src="//media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10698-017-9302-7/MediaObjects/10698_2017_9302_Fig6_HTML.gif" alt="figure 6" loading="lazy"></picture></a></div><div class="c-article-section__figure-description" data-test="bottom-caption" id="figure-6-desc"><p>The normalized I<sub>P</sub> (top) and E<sub>A</sub> (bottom) values for atoms representing the chemical elements from Groups 1, 2, 17 and 18 (<i>cf.</i> text for details of normalization). Since the E<sub>A</sub> values are predominantly null for the elements of Groups 2 and 18, and the normalization to the value shown by the first member is not possible, we have not plotted these values here. The <b>c</b>, <b>b</b> and <b>a</b> variants from Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig5">5</a>, are explicitly showed</p></div></div><div class="u-text-right u-hide-print"><a class="c-article__pill-button" data-test="article-link" data-track="click" data-track-label="button" data-track-action="view figure" href="/article/10.1007/s10698-017-9302-7/figures/6" data-track-dest="link:Figure6 Full size image" aria-label="Full size image figure 6" rel="nofollow"><span>Full size image</span><svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-chevron-right-small"></use></svg></a></div></figure></div> </div><div class="c-article-section__content"><p>Let us begin the discussion of the trends in the first ionization potential. Placement of H over Li and He over Be leads to the following picture: the normalized I<sub>P</sub> drops considerably between H and Li and between He and Be (emphasizing the well-known substantial discrepancy between the properties of elements from Period 1 and Period 2), and then drops more smoothly for the subsequent periods (only Period 7 elements slightly bend this trend as compared to their Period 6 counterparts due to well-known relativistic effects). Similar trends is seen for Groups 17 and 18, albeit the fall of normalized I<sub>P</sub> is not as dramatic (recall, we now start with Period 2 elements, F and Ne, as the first members of their series). Remarkably, Group 1 and Group 2 elements show (quantitatively) very similar behaviour, so do Group 17 and Group 18 elements. This emphasizes the fact that for the former it is the s shell which is ionized, while for the latter it is the p shell. Precisely this argument has been used by Bent (Bent <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2006" title="Bent, H.: New ideas in chemistry from fresh energy for the periodic law. AuthorHouse, Bloomington (2006)" href="/article/10.1007/s10698-017-9302-7#ref-CR7" id="ref-link-section-d55432524e1134">2006</a>) who was fierce advocate of situation C) in Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig5">5</a>.</p></div><div class="c-article-section__content"><p>If, however, we accept that H should be placed together with halogens while helium should join other noble gases, the picture of normalized I<sub>P</sub> changes substantially. Although the normalized I<sub>P</sub> values fall as before with the increase of the Period number, yet there appear marked (quantitative) differences between the first two groups of elements (Groups 1 and 2), as well as between the latter two (Groups 17 and 18).</p></div><div class="c-article-section__content"><p>Finally, if we decide to follow the traditional placement with H in Group 1 and He in Group 18, the discrepancies between the trends seen for Group and Group 2 are even larger than in the previously discussed case. And the (natural) large drop of the normalized I<sub>P</sub> between H and Li is not seen for Group 2, since He is no longer in this Group.</p></div><div class="c-article-section__content"><p>The supplemental analysis of the normalized E<sub>A</sub> concerns two major situations: H is placed in Group or in Group 17. The placement of He does not matter here since its E<sub>A</sub> is null, and therefore it fits either Group 2 (with Be showing the same value) or Group 18 (Ne having the same feature). Among the two situations the one with H placed in Group 1 seems more natural, as the normalized E<sub>A</sub> value drops slowly for Group 1 elements (again, except the reversed trend from Period 6 to Period 7 due to relativistic effects). However, if H is placed in Group 17, as advocated by some, the normalized E<sub>A</sub> skyrockets up to nearly 5, since the values for F and Cl are much larger than that for H. Thus, the traditional placement of H in Group 1 does indeed have more pros than cons, and more supporters.</p></div><div class="c-article-section__content"><p>Taking this altogether, it seems that placement of H over Li and He over Be leads to the most balanced picture, with natural trends for both the normalized I<sub>P</sub> and the normalized E<sub>A</sub> as one goes down the four respective Groups of the Periodic Chart.</p></div><div class="c-article-section__content"><p>So, what do we have to lose by placing He over Be? Some Pros and Cons are displayed in Table <a data-track="click" data-track-label="link" data-track-action="table anchor" href="/article/10.1007/s10698-017-9302-7#Tab1">1</a>.</p><div class="c-article-table" data-test="inline-table" data-container-section="table" id="table-1"><figure><figcaption class="c-article-table__figcaption"><b id="Tab1" data-test="table-caption">Table 1 Some Pros (Y) and Cons (N) of placing He above Be, or above Ne, in the Periodic Table</b></figcaption><div class="u-text-right u-hide-print"><a class="c-article__pill-button" data-test="table-link" data-track="click" data-track-action="view table" data-track-label="button" rel="nofollow" href="/article/10.1007/s10698-017-9302-7/tables/1" aria-label="Full size table 1"><span>Full size table</span><svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-chevron-right-small"></use></svg></a></div></figure></div> </div><div class="c-article-section__content"><p>As it may be seen in Table <a data-track="click" data-track-label="link" data-track-action="table anchor" href="/article/10.1007/s10698-017-9302-7#Tab1">1</a>, there are a few Pros as well as some Cons against the placement of He in Group 2. One particular Con is that with placement of He above Be, the first (historically) gaseous noble element, helium, discovered 150 years ago, would be absent from the group colloquially called “noble gases”. Simultaneously, in the traditional constructions of the periodic Chart (Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig1">1</a>), the elements with the largest I<sub>P</sub> values are expected to appear in the upper right corner; while in this case the highest-I<sub>P</sub> element, helium, would be elsewhere (this is irrelevant, though, to the left-step forms, where each block has its right top corner).</p></div><div class="c-article-section__content"><p>However, among numerous Pros for placing He above Be, one notices that such placement reproduces consistently the large gap between properties of Period 1 and 2 elements. In other words, nonmetals open Groups 1 and 2 (where mostly metals reside). Hydrogen is as much an alkali metal as helium is an alkali earth metal (as Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig6">6</a>, top left part clearly shows).</p></div><div class="c-article-section__content"><p>As Schwarz has insightfully put it in his e-mail exchange with this author (2016), there are as many versions of the Table as many features you expected to be assembled, rationalized, and taught to students. This is definitely true. There is no single way to solve this puzzle. So I am following personal idiosyncrasies here.<sup><a href="#Fn2"><span class="u-visually-hidden">Footnote </span>2</a></sup> What an experimentalist in me expects from the Periodic Table when I teach students, is that—aside from its key feature, periodicity—I may easily follow the trends of element properties as I go down the Group. And that they will make qualitative and semi-quantitative sense (while relativistic effects may be blamed for small deviations seen for the heaviest elements). And as a computational chemist, I value clear separation of elements with s, and p shells being systematically occupied by electrons. In this way also the Lewis’s doublet (for H<sup>−</sup>, He, Li<sup>+</sup>, etc.) (Lewis <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1916" title="Lewis, G.N.: The atom and the molecule. J. Am. Chem. Soc. 38(4), 762–785 (1916)" href="/article/10.1007/s10698-017-9302-7#ref-CR56" id="ref-link-section-d55432524e1505">1916</a>, <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1923" title="Lewis, G.N.: Valence and the structure of atoms and molecules. Chemical Catalog, New York (1923)" href="/article/10.1007/s10698-017-9302-7#ref-CR57" id="ref-link-section-d55432524e1508">1923</a>) is clearly separated from the octet (for F<sup>−</sup>, Ne, etc.). Thus, to my personal taste, Periodic chart should look like in Fig. <a data-track="click" data-track-label="link" data-track-action="figure anchor" href="/article/10.1007/s10698-017-9302-7#Fig5">5</a>c, revealing both the Periodic law and the more subtle tendencies associated with element properties (<i>cf.</i> Wang and Schwarz <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2009" title="Wang, S.-G., Schwarz, W.H.E.: Icon of chemistry: the periodic system of chemical elements in the new century. Angew. Chem. Int. Ed. 48(19), 2–14 (2009)" href="/article/10.1007/s10698-017-9302-7#ref-CR95" id="ref-link-section-d55432524e1520">2009</a>; Schwarz <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2013" title="Schwarz, W.H.E.: 100th anniversary of Bohr’s model of the atom. Angew. Chem. Int. Ed. 52(47), 12228–12238 (2013)" href="/article/10.1007/s10698-017-9302-7#ref-CR86" id="ref-link-section-d55432524e1523">2013</a>; Pyykkö <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2011" title="Pyykkö, P.: A suggested periodic table up to Z ≤ 172, based on Dirac-Fock calculations on atoms and ions. Phys. Chem. Chem. Phys. 13(1), 161–168 (2011)" href="/article/10.1007/s10698-017-9302-7#ref-CR73" id="ref-link-section-d55432524e1526">2011</a>, <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2012" title="Pyykkö, P.: The physics behind chemistry, and the Periodic Table. Chem. Rev. 112(1), 371–384 (2012)" href="/article/10.1007/s10698-017-9302-7#ref-CR72" id="ref-link-section-d55432524e1530">2012</a>).</p></div> </div> <section data-title="Notes"><div class="c-article-section" id="notes-section"><h2 class="c-article-section__title js-section-title js-c-reading-companion-sections-item" id="notes">Notes</h2><div class="c-article-section__content" id="notes-content"><ol class="c-article-footnote c-article-footnote--listed"><li class="c-article-footnote--listed__item" id="Fn1" data-counter="1."><div class="c-article-footnote--listed__content"><p>My impression was that you like the so-called left-step or Janet form of the Periodic Table (PT), which fulfills one of the three requirements on PTs (1. arrange the elements according to Z, 2. in a beautiful form, 3. exhibiting some chemical trends)—very well, namely symmetric beauty. A drawback of this form is that the physical origin and background of the chemical trends is less well reproduced. Of course, the final decision on the preferred form of the PT depends on the relative weights, one puts on the criteria of beauty and chemistry.</p></div></li><li class="c-article-footnote--listed__item" id="Fn2" data-counter="2."><div class="c-article-footnote--listed__content"><p>A dispute between the Reviewer (R) and the Author (A).</p><p>The presented manuscript received valuable comments during the peer-review process. They represent interesting and critical point of view. Some of them are given below, together with the responses from the author. The purpose of presenting this debate is to illustrate the complexity of argumentation which may arise when one faces the choice of the “best” place of helium in the Periodic Table.</p> <dl class="c-abbreviation_list"><dt class="c-abbreviation_list__term u-text-bold u-float-left u-pr-16" style="min-width:50px;"><dfn>R::</dfn></dt><dd class="c-abbreviation_list__description u-mb-24"> <p>There is some feeling of unreality about the debate where to put He, both in this paper and in general discussions in the literature. The viability of the Periodic Table lies in its being an organizational paper tool for similarities that accepts differences. So no inorganic chemist is put off by Si going 5- and 6-coordinate, which C remains quadrivalent, or that PbO does not dissociate into Pb + PbO2.</p> </dd><dt class="c-abbreviation_list__term u-text-bold u-float-left u-pr-16" style="min-width:50px;"><dfn>A::</dfn></dt><dd class="c-abbreviation_list__description u-mb-24"> <p>This is certainly true that the construction of the Table began as organizational paper tool (the mature form of the Table was about to serve to Mendeleyev’s students). However, the major effort beyond creation of the Table was driven by quest for similarities and not for differences. Only after the similarities helped to build the Table, one could dwell into differences. I do not share the reviewer’s feeling of unreality about the debate where to put He is such sense that this debate may be simplified to a question: which organizational paper tool is more practical and helps us to more emphasize similarities? This author claims simply that more essential similarities are better revealed by placement of He in Group 2. But there are certain, rare but important, properties, such as the very notion of inertness, which are better reflected by traditional placement of He.</p> </dd><dt class="c-abbreviation_list__term u-text-bold u-float-left u-pr-16" style="min-width:50px;"><dfn>R::</dfn></dt><dd class="c-abbreviation_list__description u-mb-24"> <p>Difference is accepted as one goes down the Table, why not accept it as one goes up, as is the case with He?</p> </dd><dt class="c-abbreviation_list__term u-text-bold u-float-left u-pr-16" style="min-width:50px;"><dfn>A::</dfn></dt><dd class="c-abbreviation_list__description u-mb-24"> <p>This is important argument. However, the departure from trends in chemical properties for heavy elements (as one goes down the Group) are well understood based on the impact of relativistic effects. However, important trends do not change for the lightest Group members, hence if we start accepting that for He, we may rebuild the entire Periodic Table to accept even more. Personally, I dislike such post-modernistic possibility.</p> </dd><dt class="c-abbreviation_list__term u-text-bold u-float-left u-pr-16" style="min-width:50px;"><dfn>R::</dfn></dt><dd class="c-abbreviation_list__description u-mb-24"> <p>I do not like the identification in italics of "chemical compounds" with neutral molecules. Charged molecules (or bonded ions from carbonate to borohydride) have a right to be called compounds. Perhaps some effort in fact might be directed to making salts of the stable noble gas ion molecular units.</p> </dd><dt class="c-abbreviation_list__term u-text-bold u-float-left u-pr-16" style="min-width:50px;"><dfn>A::</dfn></dt><dd class="c-abbreviation_list__description u-mb-24"> <p>The referee is right about the effort of making salts of the stable noble gas ion molecular units – this was discussed extensively by Christe (and it is cited here). Also, HArF may be viewed as a salt of ArH+, as this is the most important resonance structure of this molecule. But this does not change the attitude of most chemists towards ions – since you cannot isolate 1 mol of them in the bottle, they are not compounds. They are molecules, but not compounds. The ArH+ cation has been flying around for 100 years in the chambers of the mass spectrometers, as it is very stable. Yet this is neutral HArF which is considered by the community to be the first isolable compound of Ar. Otherwise, no one would pay attention to this discovery.</p> <p>I understand the reviewer’s hesitance to discard ions as “compounds”; but I think this is a matter of nomenclature. I agree with those who restrictively claim that only neutral species may be called compounds. And also with those who agree that ions have chemistry (obviously!), and mass spectroscopists do genuine chemistry. But there is no contradiction between these two claims!</p> </dd><dt class="c-abbreviation_list__term u-text-bold u-float-left u-pr-16" style="min-width:50px;"><dfn>R::</dfn></dt><dd class="c-abbreviation_list__description u-mb-24"> <p>There might be some chemistry of He anion, which is not bound in its ground state, but one excited state has a reasonable lifetime.</p> </dd><dt class="c-abbreviation_list__term u-text-bold u-float-left u-pr-16" style="min-width:50px;"><dfn>A::</dfn></dt><dd class="c-abbreviation_list__description u-mb-24"> <p>I agree but I would not like to dwell into excited states. Excited states always have rich chemistry, so if one examines neutral He atom (with its unreactive doublet) and excites it to the 1s12s1 configuration, it may even form a doubly bonded He2 molecule! Indeed, the diagram of electronic states of He2 reveals many bonded excited states. But this is usually not discussed while thinking of the element’s position in the Table, since any element shows rich chemistry in its excited states. Excited He and Ne are not inert at all. While the Table reveals mostly the ground state properties.</p> </dd></dl> </div></li></ol></div></div></section><div id="MagazineFulltextArticleBodySuffix"><section aria-labelledby="Bib1" data-title="References"><div class="c-article-section" id="Bib1-section"><h2 class="c-article-section__title js-section-title js-c-reading-companion-sections-item" id="Bib1">References</h2><div class="c-article-section__content" id="Bib1-content"><div data-container-section="references"><ul class="c-article-references" data-track-component="outbound reference" data-track-context="references section"><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR1">Antoniotti, P., Bronzolino, N., Grandinetti, F.: Stable compounds of the lightest noble gases: a computational investigation of RNBeNg (Ng = He, Ne, Ar). J. Phys. Chem. A <b>107</b>(16), 2974–2980 (2003)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jp027760b" data-track-item_id="10.1021/jp027760b" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjp027760b" aria-label="Article reference 1" data-doi="10.1021/jp027760b">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 1" href="http://scholar.google.com/scholar_lookup?&title=Stable%20compounds%20of%20the%20lightest%20noble%20gases%3A%20a%20computational%20investigation%20of%20RNBeNg%20%28Ng%C2%A0%3D%C2%A0He%2C%20Ne%2C%20Ar%29&journal=J.%20Phys.%20Chem.%20A&doi=10.1021%2Fjp027760b&volume=107&issue=16&pages=2974-2980&publication_year=2003&author=Antoniotti%2CP&author=Bronzolino%2CN&author=Grandinetti%2CF"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR2">Antoniotti, P., Borocci, S., Bronzolino, N., Cecchi, P., Grandinetti, F.: Noble gas anions: a theoretical investigation of FNgBN<sup>−</sup> (Ng = He–Xe). J. Phys. Chem. A <b>111</b>(40), 10144–10151 (2007)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jp0743673" data-track-item_id="10.1021/jp0743673" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjp0743673" aria-label="Article reference 2" data-doi="10.1021/jp0743673">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 2" href="http://scholar.google.com/scholar_lookup?&title=Noble%20gas%20anions%3A%20a%20theoretical%20investigation%20of%20FNgBN%E2%88%92%20%28Ng%C2%A0%3D%C2%A0He%E2%80%93Xe%29&journal=J.%20Phys.%20Chem.%20A&doi=10.1021%2Fjp0743673&volume=111&issue=40&pages=10144-10151&publication_year=2007&author=Antoniotti%2CP&author=Borocci%2CS&author=Bronzolino%2CN&author=Cecchi%2CP&author=Grandinetti%2CF"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR3">Bartlett, N.: Xenon hexafluoroplatinate (V) Xe<sup>+</sup>[PtF<sub>6</sub>]<sup>−</sup>. Proc. Chem. Soc. Lond. Chem. Soc. <b>6</b>, 218 (1962)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 3" href="http://scholar.google.com/scholar_lookup?&title=Xenon%20hexafluoroplatinate%20%28V%29%20Xe%2B%5BPtF6%5D%E2%88%92&journal=Proc.%20Chem.%20Soc.%20Lond.%20Chem.%20Soc.&volume=6&publication_year=1962&author=Bartlett%2CN"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR4">Bartlett, N., Žemva, B., Graham, L.: Redox reactions in the XeF<sub>2</sub>/platinum fluoride and XeF<sub>2</sub>/palladium fluoride systems and the conversion of XeF<sub>2</sub> to XeF<sub>4</sub> and Xe. J. Fluor. Chem. <b>7</b>(1–3), 301–320 (1976)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/S0022-1139(00)84003-8" data-track-item_id="10.1016/S0022-1139(00)84003-8" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2FS0022-1139%2800%2984003-8" aria-label="Article reference 4" data-doi="10.1016/S0022-1139(00)84003-8">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 4" href="http://scholar.google.com/scholar_lookup?&title=Redox%20reactions%20in%20the%20XeF2%2Fplatinum%20fluoride%20and%20XeF2%2Fpalladium%20fluoride%20systems%20and%20the%20conversion%20of%20XeF2%20to%20XeF4%20and%20Xe&journal=J.%20Fluor.%20Chem.&doi=10.1016%2FS0022-1139%2800%2984003-8&volume=7&issue=1%E2%80%933&pages=301-320&publication_year=1976&author=Bartlett%2CN&author=%C5%BDemva%2CB&author=Graham%2CL"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR5">Bartlett, N.: Helium can form stable bonds. Nature <b>331</b>, 487–488 (1998)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/331487a0" data-track-item_id="10.1038/331487a0" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2F331487a0" aria-label="Article reference 5" data-doi="10.1038/331487a0">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 5" href="http://scholar.google.com/scholar_lookup?&title=Helium%20can%20form%20stable%20bonds&journal=Nature&doi=10.1038%2F331487a0&volume=331&pages=487-488&publication_year=1998&author=Bartlett%2CN"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR6">Belpassi, L., Infante, I., Tarantelli, F., Visscher, L.: The chemical bond between Au(I) and the noble gases. Comparative study of NgAuF and NgAu<sup>+</sup> (Ng = Ar, Kr, Xe) by density functional and coupled cluster methods. J. Am. Chem. Soc. <b>130</b>(3), 1048–1060 (2008)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ja0772647" data-track-item_id="10.1021/ja0772647" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fja0772647" aria-label="Article reference 6" data-doi="10.1021/ja0772647">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 6" href="http://scholar.google.com/scholar_lookup?&title=The%20chemical%20bond%20between%20Au%28I%29%20and%20the%20noble%20gases.%20Comparative%20study%20of%20NgAuF%20and%20NgAu%2B%20%28Ng%C2%A0%3D%C2%A0Ar%2C%20Kr%2C%20Xe%29%20by%20density%20functional%20and%20coupled%20cluster%20methods&journal=J.%20Am.%20Chem.%20Soc.&doi=10.1021%2Fja0772647&volume=130&issue=3&pages=1048-1060&publication_year=2008&author=Belpassi%2CL&author=Infante%2CI&author=Tarantelli%2CF&author=Visscher%2CL"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR7">Bent, H.: New ideas in chemistry from fresh energy for the periodic law. AuthorHouse, Bloomington (2006)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 7" href="http://scholar.google.com/scholar_lookup?&title=New%20ideas%20in%20chemistry%20from%20fresh%20energy%20for%20the%20periodic%20law&publication_year=2006&author=Bent%2CH"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR8">Bihary, Z., Chaban, G.M., Gerber, R.B.: Stability of a chemically bound helium compound in high-pressure solid helium. J. Chem. Phys. <b>117</b>(11), 5105–5108 (2002)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1063/1.1506150" data-track-item_id="10.1063/1.1506150" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1063%2F1.1506150" aria-label="Article reference 8" data-doi="10.1063/1.1506150">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 8" href="http://scholar.google.com/scholar_lookup?&title=Stability%20of%20a%20chemically%20bound%20helium%20compound%20in%20high-pressure%20solid%20helium&journal=J.%20Chem.%20Phys.&doi=10.1063%2F1.1506150&volume=117&issue=11&pages=5105-5108&publication_year=2002&author=Bihary%2CZ&author=Chaban%2CGM&author=Gerber%2CRB"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR9">Borocci, S., Bronzolino, N., Grandinetti, F.: Noble gas–sulfur anions: a theoretical investigation of FNgS − (Ng = He, Ar, Kr, Xe). Chem. Phys. Lett. <b>458</b>(1–3), 48–53 (2008)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/j.cplett.2008.04.098" data-track-item_id="10.1016/j.cplett.2008.04.098" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2Fj.cplett.2008.04.098" aria-label="Article reference 9" data-doi="10.1016/j.cplett.2008.04.098">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 9" href="http://scholar.google.com/scholar_lookup?&title=Noble%20gas%E2%80%93sulfur%20anions%3A%20a%20theoretical%20investigation%20of%20FNgS%C2%A0%E2%88%92%C2%A0%28Ng%C2%A0%3D%C2%A0He%2C%20Ar%2C%20Kr%2C%20Xe%29&journal=Chem.%20Phys.%20Lett.&doi=10.1016%2Fj.cplett.2008.04.098&volume=458&issue=1%E2%80%933&pages=48-53&publication_year=2008&author=Borocci%2CS&author=Bronzolino%2CN&author=Grandinetti%2CF"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR10">Borocci, S., Bronzolino, N., Giordani, M., Grandinetti, F.: Cationic noble gas hydrides: a theoretical investigation of dinuclear HNgFNgH<sup>+</sup> (Ng = He − Xe). J. Phys. Chem. A <b>114</b>(27), 7382–7390 (2010)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jp102018n" data-track-item_id="10.1021/jp102018n" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjp102018n" aria-label="Article reference 10" data-doi="10.1021/jp102018n">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 10" href="http://scholar.google.com/scholar_lookup?&title=Cationic%20noble%20gas%20hydrides%3A%20a%20theoretical%20investigation%20of%20dinuclear%20HNgFNgH%2B%20%28Ng%C2%A0%3D%C2%A0He%C2%A0%E2%88%92%C2%A0Xe%29&journal=J.%20Phys.%20Chem.%20A&doi=10.1021%2Fjp102018n&volume=114&issue=27&pages=7382-7390&publication_year=2010&author=Borocci%2CS&author=Bronzolino%2CN&author=Giordani%2CM&author=Grandinetti%2CF"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR11">Brock, D. S., Schrobilgen, G. J., Žemva, B.: Noble-gas chemistry. In: Reedijk, J., Poeppelmeier, K. (eds.) Comprehensive Inorganic Chemistry II (Second Edition): From Elements to Applications, vol. 1, pp. 755–822 (2013). <a href="http://www.sciencedirect.com/science/referenceworks/9780080965291" data-track="click_references" data-track-action="external reference" data-track-value="external reference" data-track-label="http://www.sciencedirect.com/science/referenceworks/9780080965291">http://www.sciencedirect.com/science/referenceworks/9780080965291</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR12">Cappelletti, D., Bartocci, A., Grandinetti, F., Falcinelli, S., Belpassi, L., Tarantelli, F., Pirani, F.: Experimental evidence of chemical components in the bonding of helium and neon with neutral molecules. Chem. Eur. J. <b>21</b>(16), 6234–6240 (2015)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1002/chem.201406103" data-track-item_id="10.1002/chem.201406103" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1002%2Fchem.201406103" aria-label="Article reference 12" data-doi="10.1002/chem.201406103">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 12" href="http://scholar.google.com/scholar_lookup?&title=Experimental%20evidence%20of%20chemical%20components%20in%20the%20bonding%20of%20helium%20and%20neon%20with%20neutral%20molecules&journal=Chem.%20Eur.%20J.&doi=10.1002%2Fchem.201406103&volume=21&issue=16&pages=6234-6240&publication_year=2015&author=Cappelletti%2CD&author=Bartocci%2CA&author=Grandinetti%2CF&author=Falcinelli%2CS&author=Belpassi%2CL&author=Tarantelli%2CF&author=Pirani%2CF"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR13">Christe, K.O., Wilson, W.W.: Perfluorammonium and alkali-metal salts of the heptafluoroxenon(VI) and octafluoroxenon(VI) anions. Inorg. Chem. <b>21</b>(12), 4113–4117 (1982)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ic00142a001" data-track-item_id="10.1021/ic00142a001" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fic00142a001" aria-label="Article reference 13" data-doi="10.1021/ic00142a001">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 13" href="http://scholar.google.com/scholar_lookup?&title=Perfluorammonium%20and%20alkali-metal%20salts%20of%20the%20heptafluoroxenon%28VI%29%20and%20octafluoroxenon%28VI%29%20anions&journal=Inorg.%20Chem.&doi=10.1021%2Fic00142a001&volume=21&issue=12&pages=4113-4117&publication_year=1982&author=Christe%2CKO&author=Wilson%2CWW"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR14">Christe, K.O., Curtis, E.C., Dixon, D.A., Mercier, H.P., Sanders, J.C.P., Schrobilgen, G.J.: The pentafluoroxenate(IV) anion, XeF<sub>5</sub> <sup>−</sup>: the first example of a pentagonal planar AX<sub>5</sub> species. J. Am. Chem. Soc. <b>113</b>(9), 3351–3361 (1991)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ja00009a021" data-track-item_id="10.1021/ja00009a021" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fja00009a021" aria-label="Article reference 14" data-doi="10.1021/ja00009a021">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 14" href="http://scholar.google.com/scholar_lookup?&title=The%20pentafluoroxenate%28IV%29%20anion%2C%20XeF5%20%E2%88%92%3A%20the%20first%20example%20of%20a%20pentagonal%20planar%20AX5%20species&journal=J.%20Am.%20Chem.%20Soc.&doi=10.1021%2Fja00009a021&volume=113&issue=9&pages=3351-3361&publication_year=1991&author=Christe%2CKO&author=Curtis%2CEC&author=Dixon%2CDA&author=Mercier%2CHP&author=Sanders%2CJCP&author=Schrobilgen%2CGJ"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR15">Christe, K.O.: A renaissance in noble gas chemistry. Angew. Chem. Int. Ed. Engl. <b>40</b>(8), 1419–1421 (2001)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1002/1521-3773(20010417)40:8<1419::AID-ANIE1419>3.0.CO;2-J" data-track-item_id="10.1002/1521-3773(20010417)40:8<1419::AID-ANIE1419>3.0.CO;2-J" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1002%2F1521-3773%2820010417%2940%3A8%3C1419%3A%3AAID-ANIE1419%3E3.0.CO%3B2-J" aria-label="Article reference 15" data-doi="10.1002/1521-3773(20010417)40:8<1419::AID-ANIE1419>3.0.CO;2-J">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 15" href="http://scholar.google.com/scholar_lookup?&title=A%20renaissance%20in%20noble%20gas%20chemistry&journal=Angew.%20Chem.%20Int.%20Ed.%20Engl.&doi=10.1002%2F1521-3773%2820010417%2940%3A8%3C1419%3A%3AAID-ANIE1419%3E3.0.CO%3B2-J&volume=40&issue=8&pages=1419-1421&publication_year=2001&author=Christe%2CKO"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR16">Craciun, R., Picone, D., Long, R.T., Li, S., Dixon, D.A., Peterson, K.A., Christe, K.O.: Third row transition metal hexafluorides, extraordinary oxidizers, and Lewis acids: electron affinities, fluoride affinities, and heats of formation of WF<sub>6</sub>, ReF<sub>6</sub>, OsF<sub>6</sub>, IrF<sub>6</sub>, PtF<sub>6</sub>, and AuF<sub>6</sub>. Inorg. Chem. <b>49</b>(3), 1056–1070 (2010)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ic901967h" data-track-item_id="10.1021/ic901967h" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fic901967h" aria-label="Article reference 16" data-doi="10.1021/ic901967h">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 16" href="http://scholar.google.com/scholar_lookup?&title=Third%20row%20transition%20metal%20hexafluorides%2C%20extraordinary%20oxidizers%2C%20and%20Lewis%20acids%3A%20electron%20affinities%2C%20fluoride%20affinities%2C%20and%20heats%20of%20formation%20of%20WF6%2C%20ReF6%2C%20OsF6%2C%20IrF6%2C%20PtF6%2C%20and%20AuF6&journal=Inorg.%20Chem.&doi=10.1021%2Fic901967h&volume=49&issue=3&pages=1056-1070&publication_year=2010&author=Craciun%2CR&author=Picone%2CD&author=Long%2CRT&author=Li%2CS&author=Dixon%2CDA&author=Peterson%2CKA&author=Christe%2CKO"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR17">Cunje, A., Baranov, V.I., Ling, Y., Hopkinson, A.C., Bohme, D.K.: Bonding of rare-gas atoms to Si in reactions of rare gases with SiF<sub>3</sub> <sup>+</sup>. J. Phys. Chem. A <b>105</b>(49), 11073–11079 (2001)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jp011908u" data-track-item_id="10.1021/jp011908u" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjp011908u" aria-label="Article reference 17" data-doi="10.1021/jp011908u">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 17" href="http://scholar.google.com/scholar_lookup?&title=Bonding%20of%20rare-gas%20atoms%20to%20Si%20in%20reactions%20of%20rare%20gases%20with%20SiF3%20%2B&journal=J.%20Phys.%20Chem.%20A&doi=10.1021%2Fjp011908u&volume=105&issue=49&pages=11073-11079&publication_year=2001&author=Cunje%2CA&author=Baranov%2CVI&author=Ling%2CY&author=Hopkinson%2CAC&author=Bohme%2CDK"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR18">Dewaele, A., Worth, N., Pickard, C.J., Needs, R.J., Pascarelli, S., Mathon, O., Mezouar, M., Irifune, T.: Synthesis and stability of xenon oxides Xe<sub>2</sub>O<sub>5</sub> and Xe<sub>3</sub>O<sub>2</sub> under pressure. Nat. Chem. <b>8</b>(8), 784–790 (2016)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/nchem.2528" data-track-item_id="10.1038/nchem.2528" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2Fnchem.2528" aria-label="Article reference 18" data-doi="10.1038/nchem.2528">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 18" href="http://scholar.google.com/scholar_lookup?&title=Synthesis%20and%20stability%20of%20xenon%20oxides%20Xe2O5%20and%20Xe3O2%20under%20pressure&journal=Nat.%20Chem.&doi=10.1038%2Fnchem.2528&volume=8&issue=8&pages=784-790&publication_year=2016&author=Dewaele%2CA&author=Worth%2CN&author=Pickard%2CCJ&author=Needs%2CRJ&author=Pascarelli%2CS&author=Mathon%2CO&author=Mezouar%2CM&author=Irifune%2CT"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR19">Dixon, D.A., Wang, T.H., Grant, D.J., Peterson, K.A., Christe, K.O., Schrobilgen, G.J.: Heats of formation of krypton fluorides and stability predictions for KrF<sub>4</sub> and KrF<sub>6</sub> from high level electronic structure calculations. Inorg. Chem. <b>46</b>(23), 10016–10021 (2007)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ic701313h" data-track-item_id="10.1021/ic701313h" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fic701313h" aria-label="Article reference 19" data-doi="10.1021/ic701313h">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 19" href="http://scholar.google.com/scholar_lookup?&title=Heats%20of%20formation%20of%20krypton%20fluorides%20and%20stability%20predictions%20for%20KrF4%20and%20KrF6%20from%20high%20level%20electronic%20structure%20calculations&journal=Inorg.%20Chem.&doi=10.1021%2Fic701313h&volume=46&issue=23&pages=10016-10021&publication_year=2007&author=Dixon%2CDA&author=Wang%2CTH&author=Grant%2CDJ&author=Peterson%2CKA&author=Christe%2CKO&author=Schrobilgen%2CGJ"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR20">Dong, X., Oganov, A.R., Goncharov, A.F., Stavrou, E., Lobanov, S., Saleh, G., Qian, G.-R., Zhu, Q., Gatti, C., Deringer, V.L., Dronskowski, R., Zhou, X.-F., Prakapenka, V., Konôpková, Z., Popov, I.A., Boldyrev, A.I., Wang, H.-T.: Stable compound of helium and sodium at high pressure. Nat. Chem. <b>9</b>, 440–445 (2017)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/nchem.2716" data-track-item_id="10.1038/nchem.2716" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2Fnchem.2716" aria-label="Article reference 20" data-doi="10.1038/nchem.2716">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 20" href="http://scholar.google.com/scholar_lookup?&title=Stable%20compound%20of%20helium%20and%20sodium%20at%20high%20pressure&journal=Nat.%20Chem.&doi=10.1038%2Fnchem.2716&volume=9&pages=440-445&publication_year=2017&author=Dong%2CX&author=Oganov%2CAR&author=Goncharov%2CAF&author=Stavrou%2CE&author=Lobanov%2CS&author=Saleh%2CG&author=Qian%2CG-R&author=Zhu%2CQ&author=Gatti%2CC&author=Deringer%2CVL&author=Dronskowski%2CR&author=Zhou%2CX-F&author=Prakapenka%2CV&author=Kon%C3%B4pkov%C3%A1%2CZ&author=Popov%2CIA&author=Boldyrev%2CAI&author=Wang%2CH-T"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR21">Evans, C.J., Gerry, M.C.L.: The microwave spectra and structures of Ar–AgX (X = F, Cl, Br). J. Chem. Phys. <b>112</b>(3), 1321–1329 (2000)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1063/1.480684" data-track-item_id="10.1063/1.480684" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1063%2F1.480684" aria-label="Article reference 21" data-doi="10.1063/1.480684">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 21" href="http://scholar.google.com/scholar_lookup?&title=The%20microwave%20spectra%20and%20structures%20of%20Ar%E2%80%93AgX%20%28X%C2%A0%3D%C2%A0F%2C%20Cl%2C%20Br%29&journal=J.%20Chem.%20Phys.&doi=10.1063%2F1.480684&volume=112&issue=3&pages=1321-1329&publication_year=2000&author=Evans%2CCJ&author=Gerry%2CMCL"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR22">Francl, M.: Table manners. Nat. Chem. <b>1</b>(2), 97–98 (2009)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/nchem.183" data-track-item_id="10.1038/nchem.183" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2Fnchem.183" aria-label="Article reference 22" data-doi="10.1038/nchem.183">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 22" href="http://scholar.google.com/scholar_lookup?&title=Table%20manners&journal=Nat.%20Chem.&doi=10.1038%2Fnchem.183&volume=1&issue=2&pages=97-98&publication_year=2009&author=Francl%2CM"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR25">Frenking, G., Cremer, D.: The chemistry of the noble gas elements helium, neon, and argon—experimental facts and theoretical predictions. Struct. Bonding <b>73</b>, 17 (1990)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="noopener" data-track-label="10.1007/3-540-52124-0_2" data-track-item_id="10.1007/3-540-52124-0_2" data-track-value="article reference" data-track-action="article reference" href="https://link.springer.com/doi/10.1007/3-540-52124-0_2" aria-label="Article reference 23" data-doi="10.1007/3-540-52124-0_2">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 23" href="http://scholar.google.com/scholar_lookup?&title=The%20chemistry%20of%20the%20noble%20gas%20elements%20helium%2C%20neon%2C%20and%20argon%E2%80%94experimental%20facts%20and%20theoretical%20predictions&journal=Struct.%20Bonding&doi=10.1007%2F3-540-52124-0_2&volume=73&publication_year=1990&author=Frenking%2CG&author=Cremer%2CD"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR23">Frenking, G., Koch, W., Gauss, J., Cremer, D.: Stabilities and nature of the attractive interactions in HeBeO, NeBeO, and ArBeO and a comparison with analogs NGLiF, NGBN, and NGLiH (NG = He, Ar). A theoretical investigation. J. Am. Chem. Soc. <b>110</b>(24), 8007–8016 (1988)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ja00232a009" data-track-item_id="10.1021/ja00232a009" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fja00232a009" aria-label="Article reference 24" data-doi="10.1021/ja00232a009">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 24" href="http://scholar.google.com/scholar_lookup?&title=Stabilities%20and%20nature%20of%20the%20attractive%20interactions%20in%20HeBeO%2C%20NeBeO%2C%20and%20ArBeO%20and%20a%20comparison%20with%20analogs%20NGLiF%2C%20NGBN%2C%20and%20NGLiH%20%28NG%C2%A0%3D%C2%A0He%2C%20Ar%29.%20A%20theoretical%20investigation&journal=J.%20Am.%20Chem.%20Soc.&doi=10.1021%2Fja00232a009&volume=110&issue=24&pages=8007-8016&publication_year=1988&author=Frenking%2CG&author=Koch%2CW&author=Gauss%2CJ&author=Cremer%2CD"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR24">Frenking, G., Koch, W., Deakyne, C.A., Liebman, J.F., Bartlett, N.: The ArF<sup>+</sup> cation. Is it stable enough to be isolated in a salt? J. Am. Chem. Soc. <b>111</b>(1), 31–33 (1989)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ja00183a005" data-track-item_id="10.1021/ja00183a005" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fja00183a005" aria-label="Article reference 25" data-doi="10.1021/ja00183a005">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 25" href="http://scholar.google.com/scholar_lookup?&title=The%20ArF%2B%20cation.%20Is%20it%20stable%20enough%20to%20be%20isolated%20in%20a%20salt%3F&journal=J.%20Am.%20Chem.%20Soc.&doi=10.1021%2Fja00183a005&volume=111&issue=1&pages=31-33&publication_year=1989&author=Frenking%2CG&author=Koch%2CW&author=Deakyne%2CCA&author=Liebman%2CJF&author=Bartlett%2CN"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR200">Frenking, G., Koch, W., Reichel, F., Cremer, D.: Light noble-gas chemistry - structures, stabilities, and bonding of helium, neon and argon compounds. J. Am. Chem. Soc. <b>112</b>(11), 4240–4256 (1990)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ja00167a020" data-track-item_id="10.1021/ja00167a020" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fja00167a020" aria-label="Article reference 26" data-doi="10.1021/ja00167a020">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 26" href="http://scholar.google.com/scholar_lookup?&title=Light%20noble-gas%20chemistry%20-%20structures%2C%20stabilities%2C%20and%20bonding%20of%20helium%2C%20neon%20and%20argon%20compounds&journal=J.%20Am.%20Chem.%20Soc.&doi=10.1021%2Fja00167a020&volume=112&issue=11&pages=4240-4256&publication_year=1988&author=Frenking%2CG&author=Koch%2CW&author=Reichel%2CF&author=Cremer%2CD"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR26">Frohn, H.J., Jakobs, S.: The pentafluorophenylxenon(II) cation: [C<sub>6</sub>F<sub>5</sub>Xe]<sup>+</sup>; the first stable system with a xenon–carbon bond. J. Chem. Soc. Chem. Commun. <b>10</b>, 625–627 (1989)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1039/C39890000625" data-track-item_id="10.1039/C39890000625" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1039%2FC39890000625" aria-label="Article reference 27" data-doi="10.1039/C39890000625">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 27" href="http://scholar.google.com/scholar_lookup?&title=The%20pentafluorophenylxenon%28II%29%20cation%3A%20%5BC6F5Xe%5D%2B%3B%20the%20first%20stable%20system%20with%20a%20xenon%E2%80%93carbon%20bond&journal=J.%20Chem.%20Soc.%20Chem.%20Commun.&doi=10.1039%2FC39890000625&volume=10&pages=625-627&publication_year=1989&author=Frohn%2CHJ&author=Jakobs%2CS"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR27">Furtado, J., De Proft, F., Geerlings, P.: The noble gases: how their electronegativity and hardness determines their chemistry. J. Phys. Chem. A <b>119</b>, 1339–1346 (2015)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jp5098876" data-track-item_id="10.1021/jp5098876" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjp5098876" aria-label="Article reference 28" data-doi="10.1021/jp5098876">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 28" href="http://scholar.google.com/scholar_lookup?&title=The%20noble%20gases%3A%20how%20their%20electronegativity%20and%20hardness%20determines%20their%20chemistry&journal=J.%20Phys.%20Chem.%20A&doi=10.1021%2Fjp5098876&volume=119&pages=1339-1346&publication_year=2015&author=Furtado%2CJ&author=Proft%2CF&author=Geerlings%2CP"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR28">Gillespie, R.J., Silvi, B.: The octet rule and hypervalence: two misunderstood concepts. Coord. Chem. Rev. <b>233–234</b>, 53–62 (2002)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/S0010-8545(02)00102-9" data-track-item_id="10.1016/S0010-8545(02)00102-9" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2FS0010-8545%2802%2900102-9" aria-label="Article reference 29" data-doi="10.1016/S0010-8545(02)00102-9">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 29" href="http://scholar.google.com/scholar_lookup?&title=The%20octet%20rule%20and%20hypervalence%3A%20two%20misunderstood%20concepts&journal=Coord.%20Chem.%20Rev.&doi=10.1016%2FS0010-8545%2802%2900102-9&volume=233%E2%80%93234&pages=53-62&publication_year=2002&author=Gillespie%2CRJ&author=Silvi%2CB"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR29">Giordani, M., Antoniotti, P., Grandinetti, F.: Stabilization of HHeF by complexation: is it a really viable strategy? Chem. Eur. J. <b>16</b>(21), 6257–6264 (2010)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1002/chem.200903282" data-track-item_id="10.1002/chem.200903282" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1002%2Fchem.200903282" aria-label="Article reference 30" data-doi="10.1002/chem.200903282">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 30" href="http://scholar.google.com/scholar_lookup?&title=Stabilization%20of%20HHeF%20by%20complexation%3A%20is%20it%20a%20really%20viable%20strategy%3F&journal=Chem.%20Eur.%20J.&doi=10.1002%2Fchem.200903282&volume=16&issue=21&pages=6257-6264&publication_year=2010&author=Giordani%2CM&author=Antoniotti%2CP&author=Grandinetti%2CF"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR30">Górski, A.W.: Morphological classification of chemical structural units. Pol. J. Chem. <b>75</b>, 159–207 (2001)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 31" href="http://scholar.google.com/scholar_lookup?&title=Morphological%20classification%20of%20chemical%20structural%20units&journal=Pol.%20J.%20Chem.&volume=75&pages=159-207&publication_year=2001&author=G%C3%B3rski%2CAW"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR31">Graham, L., Graudejus, O., Jha, N.K., Bartlett, N.: Concerning the nature of XePtF<sub>6</sub>. Coord. Chem. Rev. <b>197</b>(1), 321–334 (2000)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/S0010-8545(99)00190-3" data-track-item_id="10.1016/S0010-8545(99)00190-3" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2FS0010-8545%2899%2900190-3" aria-label="Article reference 32" data-doi="10.1016/S0010-8545(99)00190-3">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 32" href="http://scholar.google.com/scholar_lookup?&title=Concerning%20the%20nature%20of%20XePtF6&journal=Coord.%20Chem.%20Rev.&doi=10.1016%2FS0010-8545%2899%2900190-3&volume=197&issue=1&pages=321-334&publication_year=2000&author=Graham%2CL&author=Graudejus%2CO&author=Jha%2CNK&author=Bartlett%2CN"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR32">Grandinetti, F.: Neon behind the signs. Nat. Chem. <b>5</b>(5), 438 (2013)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/nchem.1631" data-track-item_id="10.1038/nchem.1631" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2Fnchem.1631" aria-label="Article reference 33" data-doi="10.1038/nchem.1631">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 33" href="http://scholar.google.com/scholar_lookup?&title=Neon%20behind%20the%20signs&journal=Nat.%20Chem.&doi=10.1038%2Fnchem.1631&volume=5&issue=5&publication_year=2013&author=Grandinetti%2CF"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR33">Grochala, W.: Atypical compounds of gases, which have been called ‘noble’. Chem. Soc. Rev. <b>36</b>(10), 1632–1655 (2007)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1039/b702109g" data-track-item_id="10.1039/b702109g" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1039%2Fb702109g" aria-label="Article reference 34" data-doi="10.1039/b702109g">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 34" href="http://scholar.google.com/scholar_lookup?&title=Atypical%20compounds%20of%20gases%2C%20which%20have%20been%20called%20%E2%80%98noble%E2%80%99&journal=Chem.%20Soc.%20Rev.&doi=10.1039%2Fb702109g&volume=36&issue=10&pages=1632-1655&publication_year=2007&author=Grochala%2CW"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR34">Grochala, W.: On chemical bonding between helium and oxygen. Pol. J. Chem. <b>83</b>(1), 87–122 (2009a)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 35" href="http://scholar.google.com/scholar_lookup?&title=On%20chemical%20bonding%20between%20helium%20and%20oxygen&journal=Pol.%20J.%20Chem.&volume=83&issue=1&pages=87-122&publication_year=2009&author=Grochala%2CW"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR35">Grochala, W.: <i>Quo vadis</i> noble gas chemistry? Talk at Universita de la Tuscia, Viterbo, Jun 9 (2009b)</p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR36">Grochala, W., Khriachtchev, L., Räsänen, M.: Noble gas chemistry. In: Khriachtchev, L. (ed.) Physics and Chemistry at Low Temperatures, pp. 421–448. Pan Stanford Publishing, Cape Town (2011)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 37" href="http://scholar.google.com/scholar_lookup?&title=Noble%20gas%20chemistry&pages=421-448&publication_year=2011&author=Grochala%2CW&author=Khriachtchev%2CL&author=R%C3%A4s%C3%A4nen%2CM"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR37">Grochala, W.: Metastable He–O bond inside a ferroelectric molecular cavity: (HeO)(LiF)<sub>2</sub>. Phys. Chem. Chem. Phys. <b>14</b>, 14860–14868 (2012)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1039/c2cp42321a" data-track-item_id="10.1039/c2cp42321a" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1039%2Fc2cp42321a" aria-label="Article reference 38" data-doi="10.1039/c2cp42321a">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 38" href="http://scholar.google.com/scholar_lookup?&title=Metastable%20He%E2%80%93O%20bond%20inside%20a%20ferroelectric%20molecular%20cavity%3A%20%28HeO%29%28LiF%292&journal=Phys.%20Chem.%20Chem.%20Phys.&doi=10.1039%2Fc2cp42321a&volume=14&pages=14860-14868&publication_year=2012&author=Grochala%2CW"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR38">Grochala, W.: Can elemental helium form chemical bonds in neutral molecules? Wissenschaftsforum Chemie 2013. Darmstadt, Germany (2013)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 39" href="http://scholar.google.com/scholar_lookup?&title=Can%20elemental%20helium%20form%20chemical%20bonds%20in%20neutral%20molecules%3F%20Wissenschaftsforum%20Chemie%202013&publication_year=2013&author=Grochala%2CW"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR39">Grochala, W.: Unpublished periodic DFT results (2014)</p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR40">Haner, J., Schrobilgen, G.J.: The chemistry of xenon(IV). Chem. Rev. <b>115</b>(2), 1255–1295 (2015)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/cr500427p" data-track-item_id="10.1021/cr500427p" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fcr500427p" aria-label="Article reference 41" data-doi="10.1021/cr500427p">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 41" href="http://scholar.google.com/scholar_lookup?&title=The%20chemistry%20of%20xenon%28IV%29&journal=Chem.%20Rev.&doi=10.1021%2Fcr500427p&volume=115&issue=2&pages=1255-1295&publication_year=2015&author=Haner%2CJ&author=Schrobilgen%2CGJ"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR41">Hermann, A., Schwerdtfeger, P.: Xenon suboxides stable under pressure. J. Phys. Chem. Lett. <b>5</b>(24), 4336–4342 (2014)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jz502230b" data-track-item_id="10.1021/jz502230b" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjz502230b" aria-label="Article reference 42" data-doi="10.1021/jz502230b">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 42" href="http://scholar.google.com/scholar_lookup?&title=Xenon%20suboxides%20stable%20under%20pressure&journal=J.%20Phys.%20Chem.%20Lett.&doi=10.1021%2Fjz502230b&volume=5&issue=24&pages=4336-4342&publication_year=2014&author=Hermann%2CA&author=Schwerdtfeger%2CP"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR42">Hope, E.G.: Coordination chemistry of the noble gases and noble gas fluorides. Coord. Chem. Rev. <b>257</b>(5–6), 902–909 (2013)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/j.ccr.2012.07.017" data-track-item_id="10.1016/j.ccr.2012.07.017" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2Fj.ccr.2012.07.017" aria-label="Article reference 43" data-doi="10.1016/j.ccr.2012.07.017">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 43" href="http://scholar.google.com/scholar_lookup?&title=Coordination%20chemistry%20of%20the%20noble%20gases%20and%20noble%20gas%20fluorides&journal=Coord.%20Chem.%20Rev.&doi=10.1016%2Fj.ccr.2012.07.017&volume=257&issue=5%E2%80%936&pages=902-909&publication_year=2013&author=Hope%2CEG"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR43">Hwang, I.C., Seidel, S., Seppelt, K.: Gold(I) and Mercury(II) Xenon Complexes. Angew. Chem. Int. Ed. <b>42</b>(36), 4392–4395 (2003)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1002/anie.200351208" data-track-item_id="10.1002/anie.200351208" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1002%2Fanie.200351208" aria-label="Article reference 44" data-doi="10.1002/anie.200351208">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 44" href="http://scholar.google.com/scholar_lookup?&title=Gold%28I%29%20and%20Mercury%28II%29%20Xenon%20Complexes&journal=Angew.%20Chem.%20Int.%20Ed.&doi=10.1002%2Fanie.200351208&volume=42&issue=36&pages=4392-4395&publication_year=2003&author=Hwang%2CIC&author=Seidel%2CS&author=Seppelt%2CK"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR44">Janet, C.: Essais de classification hélicoïdale des éléments chimiques. Imprimerie Départementale de l’Oise, Beauvais (1928a)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 45" href="http://scholar.google.com/scholar_lookup?&title=Essais%20de%20classification%20h%C3%A9lico%C3%AFdale%20des%20%C3%A9l%C3%A9ments%20chimiques&publication_year=1928&author=Janet%2CC"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR45">Janet, C.: La classification hélicoïdale des éléments chimiques. Imprimerie Départementale de l’Oise, Beauvais (1928b)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 46" href="http://scholar.google.com/scholar_lookup?&title=La%20classification%20h%C3%A9lico%C3%AFdale%20des%20%C3%A9l%C3%A9ments%20chimiques&publication_year=1928&author=Janet%2CC"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR46">Janet, C.: The helicoidal classification of the elements. Chem. News <b>138</b>(372–374), 388–393 (1929)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 47" href="http://scholar.google.com/scholar_lookup?&title=The%20helicoidal%20classification%20of%20the%20elements&journal=Chem.%20News&volume=138&issue=372%E2%80%93374&pages=388-393&publication_year=1929&author=Janet%2CC"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR47">Khriachtchev, L., Pettersson, M., Runeberg, N., Lundell, J., Räsänen, M.: A stable argon compound. Nature <b>406</b>, 874–876 (2000)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/35022551" data-track-item_id="10.1038/35022551" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2F35022551" aria-label="Article reference 48" data-doi="10.1038/35022551">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 48" href="http://scholar.google.com/scholar_lookup?&title=A%20stable%20argon%20compound&journal=Nature&doi=10.1038%2F35022551&volume=406&pages=874-876&publication_year=2000&author=Khriachtchev%2CL&author=Pettersson%2CM&author=Runeberg%2CN&author=Lundell%2CJ&author=R%C3%A4s%C3%A4nen%2CM"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR48">Kim, M., Debessai, M., Yoo, C.-S.: Two- and three-dimensional extended solids and metallization of compressed XeF<sub>2</sub>. Nat. Chem. <b>2</b>(9), 784–788 (2010)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/nchem.724" data-track-item_id="10.1038/nchem.724" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2Fnchem.724" aria-label="Article reference 49" data-doi="10.1038/nchem.724">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 49" href="http://scholar.google.com/scholar_lookup?&title=Two-%20and%20three-dimensional%20extended%20solids%20and%20metallization%20of%20compressed%20XeF2&journal=Nat.%20Chem.&doi=10.1038%2Fnchem.724&volume=2&issue=9&pages=784-788&publication_year=2010&author=Kim%2CM&author=Debessai%2CM&author=Yoo%2CC-S"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR49">Koch, W., Collins, J.R., Frenking, G.: Are there neutral helium compounds which are stable in their ground state? A theoretical investigation of HeBCH and HeBeO. Chem. Phys. Lett. <b>132</b>(3), 330–333 (1986)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/0009-2614(86)80134-8" data-track-item_id="10.1016/0009-2614(86)80134-8" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2F0009-2614%2886%2980134-8" aria-label="Article reference 50" data-doi="10.1016/0009-2614(86)80134-8">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 50" href="http://scholar.google.com/scholar_lookup?&title=Are%20there%20neutral%20helium%20compounds%20which%20are%20stable%20in%20their%20ground%20state%3F%20A%20theoretical%20investigation%20of%20HeBCH%20and%20HeBeO&journal=Chem.%20Phys.%20Lett.&doi=10.1016%2F0009-2614%2886%2980134-8&volume=132&issue=3&pages=330-333&publication_year=1986&author=Koch%2CW&author=Collins%2CJR&author=Frenking%2CG"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR50">Kurzydłowski, D., Zaleski-Ejgierd, P., Grochala, W., Hoffmann, R.: Freezing in resonance structures for better packing: XeF<sub>2</sub> becomes (XeF<sup>+</sup>)(F<sup>−</sup>) at large compression. Inorg. Chem. <b>50</b>(8), 3832–3840 (2011)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ic200371a" data-track-item_id="10.1021/ic200371a" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fic200371a" aria-label="Article reference 51" data-doi="10.1021/ic200371a">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 51" href="http://scholar.google.com/scholar_lookup?&title=Freezing%20in%20resonance%20structures%20for%20better%20packing%3A%20XeF2%20becomes%20%28XeF%2B%29%28F%E2%88%92%29%20at%20large%20compression&journal=Inorg.%20Chem.&doi=10.1021%2Fic200371a&volume=50&issue=8&pages=3832-3840&publication_year=2011&author=Kurzyd%C5%82owski%2CD&author=Zaleski-Ejgierd%2CP&author=Grochala%2CW&author=Hoffmann%2CR"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR51">Kurzydłowski, D., Zaleski-Ejgierd, P.: High-pressure stabilization of argon fluorides. Phys. Chem. Chem. Phys. <b>18</b>(4), 2309–2313 (2016)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1039/C5CP05725F" data-track-item_id="10.1039/C5CP05725F" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1039%2FC5CP05725F" aria-label="Article reference 52" data-doi="10.1039/C5CP05725F">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 52" href="http://scholar.google.com/scholar_lookup?&title=High-pressure%20stabilization%20of%20argon%20fluorides&journal=Phys.%20Chem.%20Chem.%20Phys.&doi=10.1039%2FC5CP05725F&volume=18&issue=4&pages=2309-2313&publication_year=2016&author=Kurzyd%C5%82owski%2CD&author=Zaleski-Ejgierd%2CP"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR52">Laszlo, P., Schrobilgen, G.J.: One or several pioneers? The discovery of noble-gas compounds. Angew. Chem. Int. Ed. Engl. <b>27</b>(4), 479–489 (1988)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1002/anie.198804791" data-track-item_id="10.1002/anie.198804791" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1002%2Fanie.198804791" aria-label="Article reference 53" data-doi="10.1002/anie.198804791">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 53" href="http://scholar.google.com/scholar_lookup?&title=One%20or%20several%20pioneers%3F%20The%20discovery%20of%20noble-gas%20compounds&journal=Angew.%20Chem.%20Int.%20Ed.%20Engl.&doi=10.1002%2Fanie.198804791&volume=27&issue=4&pages=479-489&publication_year=1988&author=Laszlo%2CP&author=Schrobilgen%2CGJ"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR53">Le Cornec, H.: The distribution of atomic ionization potentials reveals an unexpected Periodic Table. physchem/0201007 (2002)</p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR54">Lehmann, J.F., Mercier, H.P.A., Schrobilgen, G.J.: The chemistry of krypton. Coord. Chem. Rev. <b>233–234</b>, 1–39 (2002)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/S0010-8545(02)00202-3" data-track-item_id="10.1016/S0010-8545(02)00202-3" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2FS0010-8545%2802%2900202-3" aria-label="Article reference 55" data-doi="10.1016/S0010-8545(02)00202-3">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 55" href="http://scholar.google.com/scholar_lookup?&title=The%20chemistry%20of%20krypton&journal=Coord.%20Chem.%20Rev.&doi=10.1016%2FS0010-8545%2802%2900202-3&volume=233%E2%80%93234&pages=1-39&publication_year=2002&author=Lehmann%2CJF&author=Mercier%2CHPA&author=Schrobilgen%2CGJ"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR55">Lewars, E.G.: Modeling Marvels: Computational Anticipation of Novel Molecules, Chapter 5. Springer, Berlin (2008)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="noopener" data-track-label="10.1007/978-1-4020-6973-4" data-track-item_id="10.1007/978-1-4020-6973-4" data-track-value="book reference" data-track-action="book reference" href="https://link.springer.com/doi/10.1007/978-1-4020-6973-4" aria-label="Book reference 56" data-doi="10.1007/978-1-4020-6973-4">Book</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 56" href="http://scholar.google.com/scholar_lookup?&title=Modeling%20Marvels%3A%20Computational%20Anticipation%20of%20Novel%20Molecules%2C%20Chapter%205&doi=10.1007%2F978-1-4020-6973-4&publication_year=2008&author=Lewars%2CEG"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR56">Lewis, G.N.: The atom and the molecule. J. Am. Chem. Soc. <b>38</b>(4), 762–785 (1916)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ja02261a002" data-track-item_id="10.1021/ja02261a002" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fja02261a002" aria-label="Article reference 57" data-doi="10.1021/ja02261a002">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 57" href="http://scholar.google.com/scholar_lookup?&title=The%20atom%20and%20the%20molecule&journal=J.%20Am.%20Chem.%20Soc.&doi=10.1021%2Fja02261a002&volume=38&issue=4&pages=762-785&publication_year=1916&author=Lewis%2CGN"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR57">Lewis, G.N.: Valence and the structure of atoms and molecules. Chemical Catalog, New York (1923)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 58" href="http://scholar.google.com/scholar_lookup?&title=Valence%20and%20the%20structure%20of%20atoms%20and%20molecules&publication_year=1923&author=Lewis%2CGN"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR58">Li, T.-H., Mou, C.-H., Chen, H.-R., Hu, W.-P.: Theoretical prediction of noble gas containing anions FNgO<sup>−</sup> (Ng = He, Ar, and Kr). J. Am. Chem. Soc. <b>127</b>(25), 9241–9245 (2005)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ja051276f" data-track-item_id="10.1021/ja051276f" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fja051276f" aria-label="Article reference 59" data-doi="10.1021/ja051276f">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 59" href="http://scholar.google.com/scholar_lookup?&title=Theoretical%20prediction%20of%20noble%20gas%20containing%20anions%20FNgO%E2%88%92%20%28Ng%C2%A0%3D%C2%A0He%2C%20Ar%2C%20and%20Kr%29&journal=J.%20Am.%20Chem.%20Soc.&doi=10.1021%2Fja051276f&volume=127&issue=25&pages=9241-9245&publication_year=2005&author=Li%2CT-H&author=Mou%2CC-H&author=Chen%2CH-R&author=Hu%2CW-P"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR59">Li, X., Hermann, A., Peng, F., Lv, J., Wang, Y., Wang, H., Ma, Y.: Stable lithium argon compounds under high pressure. Sci. Rep. <b>5</b>, 16675 (2015)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/srep16675" data-track-item_id="10.1038/srep16675" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2Fsrep16675" aria-label="Article reference 60" data-doi="10.1038/srep16675">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 60" href="http://scholar.google.com/scholar_lookup?&title=Stable%20lithium%20argon%20compounds%20under%20high%20pressure&journal=Sci.%20Rep.&doi=10.1038%2Fsrep16675&volume=5&publication_year=2015&author=Li%2CX&author=Hermann%2CA&author=Peng%2CF&author=Lv%2CJ&author=Wang%2CY&author=Wang%2CH&author=Ma%2CY"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR60">Liebman, J.F., Allen, L.C.: A salt chemistry of light noble gas compounds. J. Am. Chem. Soc. <b>92</b>(12), 3539–3543 (1970)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ja00715a002" data-track-item_id="10.1021/ja00715a002" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fja00715a002" aria-label="Article reference 61" data-doi="10.1021/ja00715a002">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 61" href="http://scholar.google.com/scholar_lookup?&title=A%20salt%20chemistry%20of%20light%20noble%20gas%20compounds&journal=J.%20Am.%20Chem.%20Soc.&doi=10.1021%2Fja00715a002&volume=92&issue=12&pages=3539-3543&publication_year=1970&author=Liebman%2CJF&author=Allen%2CLC"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR61">Liu, G., Zhang, Y., Bai, X., He, F., Zhang, X., Wang, Z., Zhang, W.: Theoretical investigation of the noble gas molecular anions XAuNgX<sup>−</sup> and HAuNgX<sup>−</sup> (X = F, Cl, Br; Ng = Xe, Kr, Ar). Struct. Chem. <b>23</b>(6), 1693–1710 (2012)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="noopener" data-track-label="10.1007/s11224-012-9978-1" data-track-item_id="10.1007/s11224-012-9978-1" data-track-value="article reference" data-track-action="article reference" href="https://link.springer.com/doi/10.1007/s11224-012-9978-1" aria-label="Article reference 62" data-doi="10.1007/s11224-012-9978-1">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 62" href="http://scholar.google.com/scholar_lookup?&title=Theoretical%20investigation%20of%20the%20noble%20gas%20molecular%20anions%20XAuNgX%E2%88%92%20and%20HAuNgX%E2%88%92%20%28X%C2%A0%3D%C2%A0F%2C%20Cl%2C%20Br%3B%20Ng%C2%A0%3D%C2%A0Xe%2C%20Kr%2C%20Ar%29&journal=Struct.%20Chem.&doi=10.1007%2Fs11224-012-9978-1&volume=23&issue=6&pages=1693-1710&publication_year=2012&author=Liu%2CG&author=Zhang%2CY&author=Bai%2CX&author=He%2CF&author=Zhang%2CX&author=Wang%2CZ&author=Zhang%2CW"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR62">Liu, Y.-L., Chang, Y.-H., Li, T.-H., Chen, H.-R., Hu, W.-P.: Theoretical study on the noble-gas anions F<sup>−</sup>(NgO)<sub>n</sub> (Ng = He, Ar, and Kr). Chem. Phys. Lett. <b>439</b>(1–3), 14–17 (2007)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/j.cplett.2007.03.045" data-track-item_id="10.1016/j.cplett.2007.03.045" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2Fj.cplett.2007.03.045" aria-label="Article reference 63" data-doi="10.1016/j.cplett.2007.03.045">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 63" href="http://scholar.google.com/scholar_lookup?&title=Theoretical%20study%20on%20the%20noble-gas%20anions%20F%E2%88%92%28NgO%29n%20%28Ng%C2%A0%3D%C2%A0He%2C%20Ar%2C%20and%20Kr%29&journal=Chem.%20Phys.%20Lett.&doi=10.1016%2Fj.cplett.2007.03.045&volume=439&issue=1%E2%80%933&pages=14-17&publication_year=2007&author=Liu%2CY-L&author=Chang%2CY-H&author=Li%2CT-H&author=Chen%2CH-R&author=Hu%2CW-P"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR63">Lockyear, J.F., Douglas, K., Price, S.D., Karwowska, M., Fijałkowski, K.J., Grochala, W., Remeš, M., Roithová, J., Schröder, D.: Generation of the ArCF<sub>2</sub> <sup>2+</sup> dication. J. Phys. Chem. Lett. <b>1</b>(1), 358–362 (2010)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jz900274p" data-track-item_id="10.1021/jz900274p" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjz900274p" aria-label="Article reference 64" data-doi="10.1021/jz900274p">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 64" href="http://scholar.google.com/scholar_lookup?&title=Generation%20of%20the%20ArCF2%202%2B%20dication&journal=J.%20Phys.%20Chem.%20Lett.&doi=10.1021%2Fjz900274p&volume=1&issue=1&pages=358-362&publication_year=2010&author=Lockyear%2CJF&author=Douglas%2CK&author=Price%2CSD&author=Karwowska%2CM&author=Fija%C5%82kowski%2CKJ&author=Grochala%2CW&author=Reme%C5%A1%2CM&author=Roithov%C3%A1%2CJ&author=Schr%C3%B6der%2CD"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR64">Lovallo, C.C., Kłobukowski, M.: Transition metal-noble gas bonding: the next frontier. Chem. Phys. Lett. <b>368</b>(5), 589–593 (2003)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/S0009-2614(02)01913-9" data-track-item_id="10.1016/S0009-2614(02)01913-9" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2FS0009-2614%2802%2901913-9" aria-label="Article reference 65" data-doi="10.1016/S0009-2614(02)01913-9">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 65" href="http://scholar.google.com/scholar_lookup?&title=Transition%20metal-noble%20gas%20bonding%3A%20the%20next%20frontier&journal=Chem.%20Phys.%20Lett.&doi=10.1016%2FS0009-2614%2802%2901913-9&volume=368&issue=5&pages=589-593&publication_year=2003&author=Lovallo%2CCC&author=K%C5%82obukowski%2CM"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR65">Lundell, J., Chaban, G.M., Gerber, R.B.: Combined ab initio and anharmonic vibrational spectroscopy calculations for rare gas containing fluorohydrides, HRgF. Chem. Phys. Lett. <b>331</b>(2–4), 308–316 (2000)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/S0009-2614(00)01180-5" data-track-item_id="10.1016/S0009-2614(00)01180-5" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2FS0009-2614%2800%2901180-5" aria-label="Article reference 66" data-doi="10.1016/S0009-2614(00)01180-5">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 66" href="http://scholar.google.com/scholar_lookup?&title=Combined%20ab%20initio%20and%20anharmonic%20vibrational%20spectroscopy%20calculations%20for%20rare%20gas%20containing%20fluorohydrides%2C%20HRgF&journal=Chem.%20Phys.%20Lett.&doi=10.1016%2FS0009-2614%2800%2901180-5&volume=331&issue=2%E2%80%934&pages=308-316&publication_year=2000&author=Lundell%2CJ&author=Chaban%2CGM&author=Gerber%2CRB"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR66">McDowell, S.A.C.: Are H–He–Cl and H–Ne–Cl metastable species? A computational study. Chem. Phys. Lett. <b>342</b>(5–6), 631–635 (2001)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/S0009-2614(01)00634-0" data-track-item_id="10.1016/S0009-2614(01)00634-0" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2FS0009-2614%2801%2900634-0" aria-label="Article reference 67" data-doi="10.1016/S0009-2614(01)00634-0">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 67" href="http://scholar.google.com/scholar_lookup?&title=Are%20H%E2%80%93He%E2%80%93Cl%20and%20H%E2%80%93Ne%E2%80%93Cl%20metastable%20species%3F%20A%20computational%20study&journal=Chem.%20Phys.%20Lett.&doi=10.1016%2FS0009-2614%2801%2900634-0&volume=342&issue=5%E2%80%936&pages=631-635&publication_year=2001&author=McDowell%2CSAC"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR67">Miao, M.: React with nobility. Nat. Chem. <b>9</b>, 409–410 (2017)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/nchem.2768" data-track-item_id="10.1038/nchem.2768" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2Fnchem.2768" aria-label="Article reference 68" data-doi="10.1038/nchem.2768">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 68" href="http://scholar.google.com/scholar_lookup?&title=React%20with%20nobility&journal=Nat.%20Chem.&doi=10.1038%2Fnchem.2768&volume=9&pages=409-410&publication_year=2017&author=Miao%2CM"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR68">Naumann, D., Tyrra, W.: The first compound with a stable xenon-carbon bond: <sup>19</sup>F- and <sup>129</sup>Xe-n.m.r. spectroscopic evidence for pentafluorophenylxenon(II) fluoroborates. J. Chem. Soc. Chem. Commun. <b>1</b>, 47–50 (1989)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1039/c39890000047" data-track-item_id="10.1039/c39890000047" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1039%2Fc39890000047" aria-label="Article reference 69" data-doi="10.1039/c39890000047">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 69" href="http://scholar.google.com/scholar_lookup?&title=The%20first%20compound%20with%20a%20stable%20xenon-carbon%20bond%3A%2019F-%20and%20129Xe-n.m.r.%20spectroscopic%20evidence%20for%20pentafluorophenylxenon%28II%29%20fluoroborates&journal=J.%20Chem.%20Soc.%20Chem.%20Commun.&doi=10.1039%2Fc39890000047&volume=1&pages=47-50&publication_year=1989&author=Naumann%2CD&author=Tyrra%2CW"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR69">Novaro, O.: On the rightful place for He within the periodic table. Found. Chem. <b>10</b>, 3–12 (2008)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="noopener" data-track-label="10.1007/s10698-007-9041-2" data-track-item_id="10.1007/s10698-007-9041-2" data-track-value="article reference" data-track-action="article reference" href="https://link.springer.com/doi/10.1007/s10698-007-9041-2" aria-label="Article reference 70" data-doi="10.1007/s10698-007-9041-2">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 70" href="http://scholar.google.com/scholar_lookup?&title=On%20the%20rightful%20place%20for%20He%20within%20the%20periodic%20table&journal=Found.%20Chem.&doi=10.1007%2Fs10698-007-9041-2&volume=10&pages=3-12&publication_year=2008&author=Novaro%2CO"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR70">Pan, S., Moreno, D., Ghosh, S., Chattaraj, P.K., Merino, G.: Structure and stability of noble gas bound EX<sub>3</sub> <sup>+</sup> compounds (E = C, Ge, Sn, Pb; X = H, F, Cl, Br). J. Comput. Chem. <b>37</b>(2), 226–236 (2016)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1002/jcc.23986" data-track-item_id="10.1002/jcc.23986" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1002%2Fjcc.23986" aria-label="Article reference 71" data-doi="10.1002/jcc.23986">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 71" href="http://scholar.google.com/scholar_lookup?&title=Structure%20and%20stability%20of%20noble%20gas%20bound%20EX3%20%2B%20compounds%20%28E%C2%A0%3D%C2%A0C%2C%20Ge%2C%20Sn%2C%20Pb%3B%20X%C2%A0%3D%C2%A0H%2C%20F%2C%20Cl%2C%20Br%29&journal=J.%20Comput.%20Chem.&doi=10.1002%2Fjcc.23986&volume=37&issue=2&pages=226-236&publication_year=2016&author=Pan%2CS&author=Moreno%2CD&author=Ghosh%2CS&author=Chattaraj%2CPK&author=Merino%2CG"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR71">Pichon, A.: A letter about ‘Neon behind the signs’. Nature Chemistry blog “The Sceptical Chymist” (2013). <a href="http://blogs.nature.com/thescepticalchymist/2013/12/a-letter-about-neon-behind-the-signs.html" data-track="click_references" data-track-action="external reference" data-track-value="external reference" data-track-label="http://blogs.nature.com/thescepticalchymist/2013/12/a-letter-about-neon-behind-the-signs.html">http://blogs.nature.com/thescepticalchymist/2013/12/a-letter-about-neon-behind-the-signs.html</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR72">Pyykkö, P.: The physics behind chemistry, and the Periodic Table. Chem. Rev. <b>112</b>(1), 371–384 (2012)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/cr200042e" data-track-item_id="10.1021/cr200042e" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fcr200042e" aria-label="Article reference 73" data-doi="10.1021/cr200042e">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 73" href="http://scholar.google.com/scholar_lookup?&title=The%20physics%20behind%20chemistry%2C%20and%20the%20Periodic%20Table&journal=Chem.%20Rev.&doi=10.1021%2Fcr200042e&volume=112&issue=1&pages=371-384&publication_year=2012&author=Pyykk%C3%B6%2CP"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR73">Pyykkö, P.: A suggested periodic table up to Z ≤ 172, based on Dirac-Fock calculations on atoms and ions. Phys. Chem. Chem. Phys. <b>13</b>(1), 161–168 (2011)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1039/C0CP01575J" data-track-item_id="10.1039/C0CP01575J" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1039%2FC0CP01575J" aria-label="Article reference 74" data-doi="10.1039/C0CP01575J">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 74" href="http://scholar.google.com/scholar_lookup?&title=A%20suggested%20periodic%20table%20up%20to%20Z%C2%A0%E2%89%A4%C2%A0172%2C%20based%20on%20Dirac-Fock%20calculations%20on%20atoms%20and%20ions&journal=Phys.%20Chem.%20Chem.%20Phys.&doi=10.1039%2FC0CP01575J&volume=13&issue=1&pages=161-168&publication_year=2011&author=Pyykk%C3%B6%2CP"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR74">Renouf, E.: Noble gases. Science <b>13</b>(320), 268–270 (1901)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1126/science.13.320.268" data-track-item_id="10.1126/science.13.320.268" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1126%2Fscience.13.320.268" aria-label="Article reference 75" data-doi="10.1126/science.13.320.268">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 75" href="http://scholar.google.com/scholar_lookup?&title=Noble%20gases&journal=Science&doi=10.1126%2Fscience.13.320.268&volume=13&issue=320&pages=268-270&publication_year=1901&author=Renouf%2CE"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR75">Roithová, J., Schröder, D.: Silicon compounds of Neon and Argon. Angew. Chem. Int. Ed. <b>48</b>(46), 8788–8790 (2009)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1002/anie.200903706" data-track-item_id="10.1002/anie.200903706" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1002%2Fanie.200903706" aria-label="Article reference 76" data-doi="10.1002/anie.200903706">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 76" href="http://scholar.google.com/scholar_lookup?&title=Silicon%20compounds%20of%20Neon%20and%20Argon&journal=Angew.%20Chem.%20Int.%20Ed.&doi=10.1002%2Fanie.200903706&volume=48&issue=46&pages=8788-8790&publication_year=2009&author=Roithov%C3%A1%2CJ&author=Schr%C3%B6der%2CD"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR76">Rzepa, H.: The rational design of helium bonds. Nat. Chem. <b>2</b>(5), 390–393 (2010)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/nchem.596" data-track-item_id="10.1038/nchem.596" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2Fnchem.596" aria-label="Article reference 77" data-doi="10.1038/nchem.596">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 77" href="http://scholar.google.com/scholar_lookup?&title=The%20rational%20design%20of%20helium%20bonds&journal=Nat.%20Chem.&doi=10.1038%2Fnchem.596&volume=2&issue=5&pages=390-393&publication_year=2010&author=Rzepa%2CH"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR77">Samanta, D.: Prediction of superhalogen-stabilized noble gas compounds. J. Phys. Chem. Lett. <b>5</b>(18), 3151–3156 (2014)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jz501404h" data-track-item_id="10.1021/jz501404h" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjz501404h" aria-label="Article reference 78" data-doi="10.1021/jz501404h">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 78" href="http://scholar.google.com/scholar_lookup?&title=Prediction%20of%20superhalogen-stabilized%20noble%20gas%20compounds&journal=J.%20Phys.%20Chem.%20Lett.&doi=10.1021%2Fjz501404h&volume=5&issue=18&pages=3151-3156&publication_year=2014&author=Samanta%2CD"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR78">Scerri, E.R.: Presenting the left-step periodic table. Educ. Chem. <b>42</b>, 135–136 (2005a)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 79" href="http://scholar.google.com/scholar_lookup?&title=Presenting%20the%20left-step%20periodic%20table&journal=Educ.%20Chem.&volume=42&pages=135-136&publication_year=2005&author=Scerri%2CER"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR79">Scerri, E.: Some aspects of the metaphysics of chemistry and the nature of the elements. HYLE-Int. J. Phil. Chem. <b>11</b>, 127–145 (2005b)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 80" href="http://scholar.google.com/scholar_lookup?&title=Some%20aspects%20of%20the%20metaphysics%20of%20chemistry%20and%20the%20nature%20of%20the%20elements&journal=HYLE-Int.%20J.%20Phil.%20Chem.&volume=11&pages=127-145&publication_year=2005&author=Scerri%2CE"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR80">Scerri, E.R.: The Periodic Table: Its Story and Its Significance. Oxford University Press, Oxford (2007)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 81" href="http://scholar.google.com/scholar_lookup?&title=The%20Periodic%20Table%3A%20Its%20Story%20and%20Its%20Significance&publication_year=2007&author=Scerri%2CER"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR81">Scerri, E.R.: Periodic change. Chem. World <b>3</b>, 46–49 (2009)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 82" href="http://scholar.google.com/scholar_lookup?&title=Periodic%20change&journal=Chem.%20World&volume=3&pages=46-49&publication_year=2009&author=Scerri%2CER"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR82">Seaborg, G.T.: Prospects for further considerable extension of the periodic table. J. Chem. Educ. <b>46</b>(10), 626–634 (1969)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ed046p626" data-track-item_id="10.1021/ed046p626" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fed046p626" aria-label="Article reference 83" data-doi="10.1021/ed046p626">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 83" href="http://scholar.google.com/scholar_lookup?&title=Prospects%20for%20further%20considerable%20extension%20of%20the%20periodic%20table&journal=J.%20Chem.%20Educ.&doi=10.1021%2Fed046p626&volume=46&issue=10&pages=626-634&publication_year=1969&author=Seaborg%2CGT"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR83">Seppelt, K.: Molecular hexafluorides. Chem. Rev. <b>115</b>(2), 1296–1306 (2015)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/cr5001783" data-track-item_id="10.1021/cr5001783" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fcr5001783" aria-label="Article reference 84" data-doi="10.1021/cr5001783">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 84" href="http://scholar.google.com/scholar_lookup?&title=Molecular%20hexafluorides&journal=Chem.%20Rev.&doi=10.1021%2Fcr5001783&volume=115&issue=2&pages=1296-1306&publication_year=2015&author=Seppelt%2CK"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR84">Stewart, P.J.: Charles Janet: unrecognized genius of the periodic system. Found. Chem. <b>12</b>(1), 5–15 (2010)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="noopener" data-track-label="10.1007/s10698-008-9062-5" data-track-item_id="10.1007/s10698-008-9062-5" data-track-value="article reference" data-track-action="article reference" href="https://link.springer.com/doi/10.1007/s10698-008-9062-5" aria-label="Article reference 85" data-doi="10.1007/s10698-008-9062-5">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 85" href="http://scholar.google.com/scholar_lookup?&title=Charles%20Janet%3A%20unrecognized%20genius%20of%20the%20periodic%20system&journal=Found.%20Chem.&doi=10.1007%2Fs10698-008-9062-5&volume=12&issue=1&pages=5-15&publication_year=2010&author=Stewart%2CPJ"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR85">Schrobilgen, G.J., Moran, M.D.: Noble-gas compounds. In: Seidel, A., Bickford, M. (eds.) Kirk-Othmer Encyclopedia of Chemical Technology, vol. 16. Wiley, London (2003)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 86" href="http://scholar.google.com/scholar_lookup?&title=Noble-gas%20compounds&publication_year=2003&author=Schrobilgen%2CGJ&author=Moran%2CMD"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR86">Schwarz, W.H.E.: 100th anniversary of Bohr’s model of the atom. Angew. Chem. Int. Ed. <b>52</b>(47), 12228–12238 (2013)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1002/anie.201306024" data-track-item_id="10.1002/anie.201306024" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1002%2Fanie.201306024" aria-label="Article reference 87" data-doi="10.1002/anie.201306024">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 87" href="http://scholar.google.com/scholar_lookup?&title=100th%20anniversary%20of%20Bohr%E2%80%99s%20model%20of%20the%20atom&journal=Angew.%20Chem.%20Int.%20Ed.&doi=10.1002%2Fanie.201306024&volume=52&issue=47&pages=12228-12238&publication_year=2013&author=Schwarz%2CWHE"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR87">Seppelt, K., Seidel, S.: Xenon as a complex ligand: the tetraxenono gold(II) cation in AuXe<sub>4</sub> <sup>2+</sup>(Sb<sub>2</sub>F<sub>11</sub> <sup>−</sup>)<sub>2</sub>. Science <b>290</b>(5489), 117–118 (2000)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1126/science.290.5489.117" data-track-item_id="10.1126/science.290.5489.117" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1126%2Fscience.290.5489.117" aria-label="Article reference 88" data-doi="10.1126/science.290.5489.117">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 88" href="http://scholar.google.com/scholar_lookup?&title=Xenon%20as%20a%20complex%20ligand%3A%20the%20tetraxenono%20gold%28II%29%20cation%20in%20AuXe4%202%2B%28Sb2F11%20%E2%88%92%292&journal=Science&doi=10.1126%2Fscience.290.5489.117&volume=290&issue=5489&pages=117-118&publication_year=2000&author=Seppelt%2CK&author=Seidel%2CS"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR88">Schwarz, W. H. E. (2016) Letter to the author (July 2016)</p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR89">Stowe, T.: A Physicist’s Chart of the Chemical Elements. Instruments Research and Industry Inc., Wyncote (1989)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 90" href="http://scholar.google.com/scholar_lookup?&title=A%20Physicist%E2%80%99s%20Chart%20of%20the%20Chemical%20Elements&publication_year=1989&author=Stowe%2CT"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR90">Szarek, P., Grochala, W.: Noble gas monoxides stabilized in dipolar cavity: a theoretical study. J. Phys. Chem. A <b>119</b>(11), 2483–2489 (2015)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jp508786y" data-track-item_id="10.1021/jp508786y" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjp508786y" aria-label="Article reference 91" data-doi="10.1021/jp508786y">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 91" href="http://scholar.google.com/scholar_lookup?&title=Noble%20gas%20monoxides%20stabilized%20in%20dipolar%20cavity%3A%20a%20theoretical%20study&journal=J.%20Phys.%20Chem.%20A&doi=10.1021%2Fjp508786y&volume=119&issue=11&pages=2483-2489&publication_year=2015&author=Szarek%2CP&author=Grochala%2CW"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR201">Takayanagi, T., Wada, A.: Theoretical prediction of the lifetime of the metastable helium compound: HHeF. Chem. Phys. Lett. <b>352</b>(1–2), 91–98 (2002)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/S0009-2614(01)01436-1" data-track-item_id="10.1016/S0009-2614(01)01436-1" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2FS0009-2614%2801%2901436-1" aria-label="Article reference 92" data-doi="10.1016/S0009-2614(01)01436-1">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 92" href="http://scholar.google.com/scholar_lookup?&title=Theoretical%20prediction%20of%20the%20lifetime%20of%20the%20metastable%20helium%20compound%3A%20HHeF&journal=Chem.%20Phys.%20Lett.&doi=10.1016%2FS0009-2614%2801%2901436-1&volume=352&issue=1%E2%80%932&pages=91-98&publication_year=2002&author=Takayanagi%2CT&author=Wada%2CA"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR91">Tarantola, A.: A Periodic Table of the elements, based on the electronic structure of the atoms. (2000) chemistry/0009002</p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR92">Tarantola, A.: The Periodic Table of the elements and the ionization potentials. (2002) physchem/0201017</p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR93">Thompson, C.A., Andrews, L.: Noble-gas complexes with BeO—infrared-spectra of NG-BeO (NG = Ar, Kr, Xe). J. Am. Chem. Soc. <b>116</b>(1), 423–424 (1994)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ja00080a069" data-track-item_id="10.1021/ja00080a069" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fja00080a069" aria-label="Article reference 95" data-doi="10.1021/ja00080a069">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 95" href="http://scholar.google.com/scholar_lookup?&title=Noble-gas%20complexes%20with%20BeO%E2%80%94infrared-spectra%20of%20NG-BeO%20%28NG%C2%A0%3D%C2%A0Ar%2C%20Kr%2C%20Xe%29&journal=J.%20Am.%20Chem.%20Soc.&doi=10.1021%2Fja00080a069&volume=116&issue=1&pages=423-424&publication_year=1994&author=Thompson%2CCA&author=Andrews%2CL"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR94">Vos, W.L., Finger, L.W., Hemley, R.J., Hu, J.Z., Mao, H.K., Schouten, J.A.: A high-pressure van der Waals compound in solid nitrogen–helium mixtures. Nature <b>358</b>, 46–48 (1992)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/358046a0" data-track-item_id="10.1038/358046a0" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2F358046a0" aria-label="Article reference 96" data-doi="10.1038/358046a0">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 96" href="http://scholar.google.com/scholar_lookup?&title=A%20high-pressure%20van%20der%20Waals%20compound%20in%20solid%20nitrogen%E2%80%93helium%20mixtures&journal=Nature&doi=10.1038%2F358046a0&volume=358&pages=46-48&publication_year=1992&author=Vos%2CWL&author=Finger%2CLW&author=Hemley%2CRJ&author=Hu%2CJZ&author=Mao%2CHK&author=Schouten%2CJA"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR95">Wang, S.-G., Schwarz, W.H.E.: Icon of chemistry: the periodic system of chemical elements in the new century. Angew. Chem. Int. Ed. <b>48</b>(19), 2–14 (2009)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1002/anie.200800827" data-track-item_id="10.1002/anie.200800827" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1002%2Fanie.200800827" aria-label="Article reference 97" data-doi="10.1002/anie.200800827">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 97" href="http://scholar.google.com/scholar_lookup?&title=Icon%20of%20chemistry%3A%20the%20periodic%20system%20of%20chemical%20elements%20in%20the%20new%20century&journal=Angew.%20Chem.%20Int.%20Ed.&doi=10.1002%2Fanie.200800827&volume=48&issue=19&pages=2-14&publication_year=2009&author=Wang%2CS-G&author=Schwarz%2CWHE"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR96">Wang, X., Andrews, L., Brosi, F., Riedel, S.: Matrix infrared spectroscopy and quantum-chemical calculations for the coinage-metal fluorides: comparisons of Ar–AuF, Ne–AuF, and molecules MF<sub>2</sub> and MF<sub>3</sub>. Chem. Eur. J. <b>19</b>(4), 1397–1409 (2013)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1002/chem.201203306" data-track-item_id="10.1002/chem.201203306" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1002%2Fchem.201203306" aria-label="Article reference 98" data-doi="10.1002/chem.201203306">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 98" href="http://scholar.google.com/scholar_lookup?&title=Matrix%20infrared%20spectroscopy%20and%20quantum-chemical%20calculations%20for%20the%20coinage-metal%20fluorides%3A%20comparisons%20of%20Ar%E2%80%93AuF%2C%20Ne%E2%80%93AuF%2C%20and%20molecules%20MF2%20and%20MF3&journal=Chem.%20Eur.%20J.&doi=10.1002%2Fchem.201203306&volume=19&issue=4&pages=1397-1409&publication_year=2013&author=Wang%2CX&author=Andrews%2CL&author=Brosi%2CF&author=Riedel%2CS"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR97">Wang, Q., Wang, X.: Infrared spectra of NgBeS (Ng = Ne, Ar, Kr, Xe) and BeS<sub>2</sub> in noble-gas matrices. J. Phys. Chem. A <b>117</b>(7), 1508–1513 (2013)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jp311901a" data-track-item_id="10.1021/jp311901a" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjp311901a" aria-label="Article reference 99" data-doi="10.1021/jp311901a">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 99" href="http://scholar.google.com/scholar_lookup?&title=Infrared%20spectra%20of%20NgBeS%20%28Ng%C2%A0%3D%C2%A0Ne%2C%20Ar%2C%20Kr%2C%20Xe%29%20and%20BeS2%20in%20noble-gas%20matrices&journal=J.%20Phys.%20Chem.%20A&doi=10.1021%2Fjp311901a&volume=117&issue=7&pages=1508-1513&publication_year=2013&author=Wang%2CQ&author=Wang%2CX"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR98">Wilson, D.J.D., Marsden, C.J., von Nagy-Felsobuki, E.I.: Ab initio structures and stabilities of doubly charged diatomic metal helides for the first row transition metals. J. Phys. Chem. A <b>106</b>(32), 7348–7354 (2002)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jp0203503" data-track-item_id="10.1021/jp0203503" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjp0203503" aria-label="Article reference 100" data-doi="10.1021/jp0203503">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 100" href="http://scholar.google.com/scholar_lookup?&title=Ab%20initio%20structures%20and%20stabilities%20of%20doubly%20charged%20diatomic%20metal%20helides%20for%20the%20first%20row%20transition%20metals&journal=J.%20Phys.%20Chem.%20A&doi=10.1021%2Fjp0203503&volume=106&issue=32&pages=7348-7354&publication_year=2002&author=Wilson%2CDJD&author=Marsden%2CCJ&author=Nagy-Felsobuki%2CEI"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR99">Wong, M.W.: Prediction of a metastable helium compound: HHeF. J. Am. Chem. Soc. <b>122</b>(26), 6289–6290 (2000)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/ja9938175" data-track-item_id="10.1021/ja9938175" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fja9938175" aria-label="Article reference 101" data-doi="10.1021/ja9938175">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 101" href="http://scholar.google.com/scholar_lookup?&title=Prediction%20of%20a%20metastable%20helium%20compound%3A%20HHeF&journal=J.%20Am.%20Chem.%20Soc.&doi=10.1021%2Fja9938175&volume=122&issue=26&pages=6289-6290&publication_year=2000&author=Wong%2CMW"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR100">Zhu, Q., Jung, D.Y., Oganov, A.R., Glass, C.W., Gatti, C., Lyakhov, A.O.: Stability of xenon oxides at high pressures. Nat. Chem. <b>5</b>(1), 61–65 (2013)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/nchem.1497" data-track-item_id="10.1038/nchem.1497" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2Fnchem.1497" aria-label="Article reference 102" data-doi="10.1038/nchem.1497">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 102" href="http://scholar.google.com/scholar_lookup?&title=Stability%20of%20xenon%20oxides%20at%20high%20pressures&journal=Nat.%20Chem.&doi=10.1038%2Fnchem.1497&volume=5&issue=1&pages=61-65&publication_year=2013&author=Zhu%2CQ&author=Jung%2CDY&author=Oganov%2CAR&author=Glass%2CCW&author=Gatti%2CC&author=Lyakhov%2CAO"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR101">Zhu, L., Liu, H., Pickard, C.J., Zou, G., Ma, Y.: Reactions of xenon with iron and nickel are predicted in the Earth’s inner core. Nat. Chem. <b>6</b>(7), 644–648 (2014)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1038/nchem.1925" data-track-item_id="10.1038/nchem.1925" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1038%2Fnchem.1925" aria-label="Article reference 103" data-doi="10.1038/nchem.1925">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 103" href="http://scholar.google.com/scholar_lookup?&title=Reactions%20of%20xenon%20with%20iron%20and%20nickel%20are%20predicted%20in%20the%20Earth%E2%80%99s%20inner%20core&journal=Nat.%20Chem.&doi=10.1038%2Fnchem.1925&volume=6&issue=7&pages=644-648&publication_year=2014&author=Zhu%2CL&author=Liu%2CH&author=Pickard%2CCJ&author=Zou%2CG&author=Ma%2CY"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR102">Zou, L., Liu, Y., Boggs, J.E.: Theoretical study of RgMF (Rg = He, Ne; M = Cu, Ag, Au): bonded structures of helium. Chem. Phys. Lett. <b>482</b>(4–6), 207–210 (2009)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1016/j.cplett.2009.10.010" data-track-item_id="10.1016/j.cplett.2009.10.010" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1016%2Fj.cplett.2009.10.010" aria-label="Article reference 104" data-doi="10.1016/j.cplett.2009.10.010">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 104" href="http://scholar.google.com/scholar_lookup?&title=Theoretical%20study%20of%20RgMF%20%28Rg%C2%A0%3D%C2%A0He%2C%20Ne%3B%20M%C2%A0%3D%C2%A0Cu%2C%20Ag%2C%20Au%29%3A%20bonded%20structures%20of%20helium&journal=Chem.%20Phys.%20Lett.&doi=10.1016%2Fj.cplett.2009.10.010&volume=482&issue=4%E2%80%936&pages=207-210&publication_year=2009&author=Zou%2CL&author=Liu%2CY&author=Boggs%2CJE"> Google Scholar</a> </p></li><li class="c-article-references__item js-c-reading-companion-references-item"><p class="c-article-references__text" id="ref-CR103">Zou, W., Nori-Shargh, D., Boggs, J.E.: On the covalent character of rare gas bonding interactions: a new kind of weak interaction. J. Phys. Chem. A <b>117</b>(1), 207–212 (2013)</p><p class="c-article-references__links u-hide-print"><a data-track="click_references" rel="nofollow noopener" data-track-label="10.1021/jp3104535" data-track-item_id="10.1021/jp3104535" data-track-value="article reference" data-track-action="article reference" href="https://doi.org/10.1021%2Fjp3104535" aria-label="Article reference 105" data-doi="10.1021/jp3104535">Article</a> <a data-track="click_references" data-track-action="google scholar reference" data-track-value="google scholar reference" data-track-label="link" data-track-item_id="link" rel="nofollow noopener" aria-label="Google Scholar reference 105" href="http://scholar.google.com/scholar_lookup?&title=On%20the%20covalent%20character%20of%20rare%20gas%20bonding%20interactions%3A%20a%20new%20kind%20of%20weak%20interaction&journal=J.%20Phys.%20Chem.%20A&doi=10.1021%2Fjp3104535&volume=117&issue=1&pages=207-212&publication_year=2013&author=Zou%2CW&author=Nori-Shargh%2CD&author=Boggs%2CJE"> Google Scholar</a> </p></li></ul><p class="c-article-references__download u-hide-print"><a data-track="click" data-track-action="download citation references" data-track-label="link" rel="nofollow" href="https://citation-needed.springer.com/v2/references/10.1007/s10698-017-9302-7?format=refman&flavour=references">Download references<svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-download-medium"></use></svg></a></p></div></div></div></section></div><section data-title="Acknowledgements"><div class="c-article-section" id="Ack1-section"><h2 class="c-article-section__title js-section-title js-c-reading-companion-sections-item" id="Ack1">Acknowledgements</h2><div class="c-article-section__content" id="Ack1-content"><p>When this manuscript was in review, the author became conscious of the important contribution (Novaro <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2008" title="Novaro, O.: On the rightful place for He within the periodic table. Found. Chem. 10, 3–12 (2008)" href="/article/10.1007/s10698-017-9302-7#ref-CR69" id="ref-link-section-d55432524e1545">2008</a>) where the author advocates the placement of helium in Group 2 based on subtle nevertheless sound arguments related to many-body contributions to interatomic interactions. This paper also contains mentions to a valuable philosophical work by Scerri (Scerri <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2005b" title="Scerri, E.: Some aspects of the metaphysics of chemistry and the nature of the elements. HYLE-Int. J. Phil. Chem. 11, 127–145 (2005b)" href="/article/10.1007/s10698-017-9302-7#ref-CR79" id="ref-link-section-d55432524e1548">2005b</a>) which also escaped my attention. Simultaneously, two important references (Bartlett <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1998" title="Bartlett, N.: Helium can form stable bonds. Nature 331, 487–488 (1998)" href="/article/10.1007/s10698-017-9302-7#ref-CR5" id="ref-link-section-d55432524e1551">1998</a>; Vos et al. <a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1992" title="Vos, W.L., Finger, L.W., Hemley, R.J., Hu, J.Z., Mao, H.K., Schouten, J.A.: A high-pressure van der Waals compound in solid nitrogen–helium mixtures. Nature 358, 46–48 (1992)" href="/article/10.1007/s10698-017-9302-7#ref-CR94" id="ref-link-section-d55432524e1554">1992</a>) discussing weakly interacting He atoms (dispersive interactions in HeBeO, and vand der Waals compound of He and N<sub>2</sub>) were also brought to my attention. The author would like to acknowledge Roald Hoffmann for recommending the Bent’s book, and he appreciates the discussions with W. H. Eugen Schwarz. This research has been funded from the statutory funds of the CeNT, University of Warsaw. Prof. Davide Proseprio kindly brought to my attention the above-mentioned works by Novaro (<a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2008" title="Novaro, O.: On the rightful place for He within the periodic table. Found. Chem. 10, 3–12 (2008)" href="/article/10.1007/s10698-017-9302-7#ref-CR69" id="ref-link-section-d55432524e1560">2008</a>) and Furtado et al. (<a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 2015" title="Furtado, J., De Proft, F., Geerlings, P.: The noble gases: how their electronegativity and hardness determines their chemistry. J. Phys. Chem. A 119, 1339–1346 (2015)" href="/article/10.1007/s10698-017-9302-7#ref-CR27" id="ref-link-section-d55432524e1563">2015</a>), while Dr. Zoran Mazej reminded me of comment from Bartlett (<a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1998" title="Bartlett, N.: Helium can form stable bonds. Nature 331, 487–488 (1998)" href="/article/10.1007/s10698-017-9302-7#ref-CR5" id="ref-link-section-d55432524e1566">1998</a>) and contribution from Vos et al. (<a data-track="click" data-track-action="reference anchor" data-track-label="link" data-test="citation-ref" aria-label="Reference 1992" title="Vos, W.L., Finger, L.W., Hemley, R.J., Hu, J.Z., Mao, H.K., Schouten, J.A.: A high-pressure van der Waals compound in solid nitrogen–helium mixtures. Nature 358, 46–48 (1992)" href="/article/10.1007/s10698-017-9302-7#ref-CR94" id="ref-link-section-d55432524e1569">1992</a>).</p></div></div></section><section aria-labelledby="author-information" data-title="Author information"><div class="c-article-section" id="author-information-section"><h2 class="c-article-section__title js-section-title js-c-reading-companion-sections-item" id="author-information">Author information</h2><div class="c-article-section__content" id="author-information-content"><h3 class="c-article__sub-heading" id="affiliations">Authors and Affiliations</h3><ol class="c-article-author-affiliation__list"><li id="Aff1"><p class="c-article-author-affiliation__address">Center of New Technologies, University of Warsaw, Żwirki i Wigury 93, 02089, Warsaw, Poland</p><p class="c-article-author-affiliation__authors-list">Wojciech Grochala</p></li></ol><div class="u-js-hide u-hide-print" data-test="author-info"><span class="c-article__sub-heading">Authors</span><ol class="c-article-authors-search u-list-reset"><li id="auth-Wojciech-Grochala-Aff1"><span class="c-article-authors-search__title u-h3 js-search-name">Wojciech Grochala</span><div class="c-article-authors-search__list"><div class="c-article-authors-search__item c-article-authors-search__list-item--left"><a href="/search?dc.creator=Wojciech%20Grochala" class="c-article-button" data-track="click" data-track-action="author link - publication" data-track-label="link" rel="nofollow">View author publications</a></div><div class="c-article-authors-search__item c-article-authors-search__list-item--right"><p class="search-in-title-js c-article-authors-search__text">You can also search for this author in <span class="c-article-identifiers"><a class="c-article-identifiers__item" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=search&term=Wojciech%20Grochala" data-track="click" data-track-action="author link - pubmed" data-track-label="link" rel="nofollow">PubMed</a><span class="u-hide"> </span><a class="c-article-identifiers__item" href="http://scholar.google.co.uk/scholar?as_q=&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=any&as_sauthors=%22Wojciech%20Grochala%22&as_publication=&as_ylo=&as_yhi=&as_allsubj=all&hl=en" data-track="click" data-track-action="author link - scholar" data-track-label="link" rel="nofollow">Google Scholar</a></span></p></div></div></li></ol></div><h3 class="c-article__sub-heading" id="corresponding-author">Corresponding author</h3><p id="corresponding-author-list">Correspondence to <a id="corresp-c1" href="mailto:w.grochala@cent.uw.edu.pl">Wojciech Grochala</a>.</p></div></div></section><section data-title="Additional information"><div class="c-article-section" id="additional-information-section"><h2 class="c-article-section__title js-section-title js-c-reading-companion-sections-item" id="additional-information">Additional information</h2><div class="c-article-section__content" id="additional-information-content"><p>This work commemorates the 150th anniversary of the discovery of helium and the 120th of neon.</p></div></div></section><section data-title="Rights and permissions"><div class="c-article-section" id="rightslink-section"><h2 class="c-article-section__title js-section-title js-c-reading-companion-sections-item" id="rightslink">Rights and permissions</h2><div class="c-article-section__content" id="rightslink-content"> <p> <b>Open Access</b> This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (<a href="http://creativecommons.org/licenses/by/4.0/" rel="license">http://creativecommons.org/licenses/by/4.0/</a>), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.</p> <p class="c-article-rights"><a data-track="click" data-track-action="view rights and permissions" data-track-label="link" href="https://s100.copyright.com/AppDispatchServlet?title=On%20the%20position%20of%20helium%20and%20neon%20in%20the%20Periodic%20Table%20of%20Elements&author=Wojciech%20Grochala&contentID=10.1007%2Fs10698-017-9302-7&copyright=The%20Author%28s%29&publication=1386-4238&publicationDate=2017-11-01&publisherName=SpringerNature&orderBeanReset=true&oa=CC%20BY">Reprints and permissions</a></p></div></div></section><section aria-labelledby="article-info" data-title="About this article"><div class="c-article-section" id="article-info-section"><h2 class="c-article-section__title js-section-title js-c-reading-companion-sections-item" id="article-info">About this article</h2><div class="c-article-section__content" id="article-info-content"><div class="c-bibliographic-information"><div class="u-hide-print c-bibliographic-information__column c-bibliographic-information__column--border"><a data-crossmark="10.1007/s10698-017-9302-7" target="_blank" rel="noopener" href="https://crossmark.crossref.org/dialog/?doi=10.1007/s10698-017-9302-7" data-track="click" data-track-action="Click Crossmark" data-track-label="link" data-test="crossmark"><img loading="lazy" width="57" height="81" alt="Check for updates. Verify currency and authenticity via CrossMark" src="data:image/svg+xml;base64,<svg height="81" width="57" xmlns="http://www.w3.org/2000/svg"><g fill="none" fill-rule="evenodd"><path d="m17.35 35.45 21.3-14.2v-17.03h-21.3" fill="#989898"/><path d="m38.65 35.45-21.3-14.2v-17.03h21.3" fill="#747474"/><path d="m28 .5c-12.98 0-23.5 10.52-23.5 23.5s10.52 23.5 23.5 23.5 23.5-10.52 23.5-23.5c0-6.23-2.48-12.21-6.88-16.62-4.41-4.4-10.39-6.88-16.62-6.88zm0 41.25c-9.8 0-17.75-7.95-17.75-17.75s7.95-17.75 17.75-17.75 17.75 7.95 17.75 17.75c0 4.71-1.87 9.22-5.2 12.55s-7.84 5.2-12.55 5.2z" fill="#535353"/><path d="m41 36c-5.81 6.23-15.23 7.45-22.43 2.9-7.21-4.55-10.16-13.57-7.03-21.5l-4.92-3.11c-4.95 10.7-1.19 23.42 8.78 29.71 9.97 6.3 23.07 4.22 30.6-4.86z" fill="#9c9c9c"/><path d="m.2 58.45c0-.75.11-1.42.33-2.01s.52-1.09.91-1.5c.38-.41.83-.73 1.34-.94.51-.22 1.06-.32 1.65-.32.56 0 1.06.11 1.51.35.44.23.81.5 1.1.81l-.91 1.01c-.24-.24-.49-.42-.75-.56-.27-.13-.58-.2-.93-.2-.39 0-.73.08-1.05.23-.31.16-.58.37-.81.66-.23.28-.41.63-.53 1.04-.13.41-.19.88-.19 1.39 0 1.04.23 1.86.68 2.46.45.59 1.06.88 1.84.88.41 0 .77-.07 1.07-.23s.59-.39.85-.68l.91 1c-.38.43-.8.76-1.28.99-.47.22-1 .34-1.58.34-.59 0-1.13-.1-1.64-.31-.5-.2-.94-.51-1.31-.91-.38-.4-.67-.9-.88-1.48-.22-.59-.33-1.26-.33-2.02zm8.4-5.33h1.61v2.54l-.05 1.33c.29-.27.61-.51.96-.72s.76-.31 1.24-.31c.73 0 1.27.23 1.61.71.33.47.5 1.14.5 2.02v4.31h-1.61v-4.1c0-.57-.08-.97-.25-1.21-.17-.23-.45-.35-.83-.35-.3 0-.56.08-.79.22-.23.15-.49.36-.78.64v4.8h-1.61zm7.37 6.45c0-.56.09-1.06.26-1.51.18-.45.42-.83.71-1.14.29-.3.63-.54 1.01-.71.39-.17.78-.25 1.18-.25.47 0 .88.08 1.23.24.36.16.65.38.89.67s.42.63.54 1.03c.12.41.18.84.18 1.32 0 .32-.02.57-.07.76h-4.36c.07.62.29 1.1.65 1.44.36.33.82.5 1.38.5.29 0 .57-.04.83-.13s.51-.21.76-.37l.55 1.01c-.33.21-.69.39-1.09.53-.41.14-.83.21-1.26.21-.48 0-.92-.08-1.34-.25-.41-.16-.76-.4-1.07-.7-.31-.31-.55-.69-.72-1.13-.18-.44-.26-.95-.26-1.52zm4.6-.62c0-.55-.11-.98-.34-1.28-.23-.31-.58-.47-1.06-.47-.41 0-.77.15-1.07.45-.31.29-.5.73-.58 1.3zm2.5.62c0-.57.09-1.08.28-1.53.18-.44.43-.82.75-1.13s.69-.54 1.1-.71c.42-.16.85-.24 1.31-.24.45 0 .84.08 1.17.23s.61.34.85.57l-.77 1.02c-.19-.16-.38-.28-.56-.37-.19-.09-.39-.14-.61-.14-.56 0-1.01.21-1.35.63-.35.41-.52.97-.52 1.67 0 .69.17 1.24.51 1.66.34.41.78.62 1.32.62.28 0 .54-.06.78-.17.24-.12.45-.26.64-.42l.67 1.03c-.33.29-.69.51-1.08.65-.39.15-.78.23-1.18.23-.46 0-.9-.08-1.31-.24-.4-.16-.75-.39-1.05-.7s-.53-.69-.7-1.13c-.17-.45-.25-.96-.25-1.53zm6.91-6.45h1.58v6.17h.05l2.54-3.16h1.77l-2.35 2.8 2.59 4.07h-1.75l-1.77-2.98-1.08 1.23v1.75h-1.58zm13.69 1.27c-.25-.11-.5-.17-.75-.17-.58 0-.87.39-.87 1.16v.75h1.34v1.27h-1.34v5.6h-1.61v-5.6h-.92v-1.2l.92-.07v-.72c0-.35.04-.68.13-.98.08-.31.21-.57.4-.79s.42-.39.71-.51c.28-.12.63-.18 1.04-.18.24 0 .48.02.69.07.22.05.41.1.57.17zm.48 5.18c0-.57.09-1.08.27-1.53.17-.44.41-.82.72-1.13.3-.31.65-.54 1.04-.71.39-.16.8-.24 1.23-.24s.84.08 1.24.24c.4.17.74.4 1.04.71s.54.69.72 1.13c.19.45.28.96.28 1.53s-.09 1.08-.28 1.53c-.18.44-.42.82-.72 1.13s-.64.54-1.04.7-.81.24-1.24.24-.84-.08-1.23-.24-.74-.39-1.04-.7c-.31-.31-.55-.69-.72-1.13-.18-.45-.27-.96-.27-1.53zm1.65 0c0 .69.14 1.24.43 1.66.28.41.68.62 1.18.62.51 0 .9-.21 1.19-.62.29-.42.44-.97.44-1.66 0-.7-.15-1.26-.44-1.67-.29-.42-.68-.63-1.19-.63-.5 0-.9.21-1.18.63-.29.41-.43.97-.43 1.67zm6.48-3.44h1.33l.12 1.21h.05c.24-.44.54-.79.88-1.02.35-.24.7-.36 1.07-.36.32 0 .59.05.78.14l-.28 1.4-.33-.09c-.11-.01-.23-.02-.38-.02-.27 0-.56.1-.86.31s-.55.58-.77 1.1v4.2h-1.61zm-47.87 15h1.61v4.1c0 .57.08.97.25 1.2.17.24.44.35.81.35.3 0 .57-.07.8-.22.22-.15.47-.39.73-.73v-4.7h1.61v6.87h-1.32l-.12-1.01h-.04c-.3.36-.63.64-.98.86-.35.21-.76.32-1.24.32-.73 0-1.27-.24-1.61-.71-.33-.47-.5-1.14-.5-2.02zm9.46 7.43v2.16h-1.61v-9.59h1.33l.12.72h.05c.29-.24.61-.45.97-.63.35-.17.72-.26 1.1-.26.43 0 .81.08 1.15.24.33.17.61.4.84.71.24.31.41.68.53 1.11.13.42.19.91.19 1.44 0 .59-.09 1.11-.25 1.57-.16.47-.38.85-.65 1.16-.27.32-.58.56-.94.73-.35.16-.72.25-1.1.25-.3 0-.6-.07-.9-.2s-.59-.31-.87-.56zm0-2.3c.26.22.5.37.73.45.24.09.46.13.66.13.46 0 .84-.2 1.15-.6.31-.39.46-.98.46-1.77 0-.69-.12-1.22-.35-1.61-.23-.38-.61-.57-1.13-.57-.49 0-.99.26-1.52.77zm5.87-1.69c0-.56.08-1.06.25-1.51.16-.45.37-.83.65-1.14.27-.3.58-.54.93-.71s.71-.25 1.08-.25c.39 0 .73.07 1 .2.27.14.54.32.81.55l-.06-1.1v-2.49h1.61v9.88h-1.33l-.11-.74h-.06c-.25.25-.54.46-.88.64-.33.18-.69.27-1.06.27-.87 0-1.56-.32-2.07-.95s-.76-1.51-.76-2.65zm1.67-.01c0 .74.13 1.31.4 1.7.26.38.65.58 1.15.58.51 0 .99-.26 1.44-.77v-3.21c-.24-.21-.48-.36-.7-.45-.23-.08-.46-.12-.7-.12-.45 0-.82.19-1.13.59-.31.39-.46.95-.46 1.68zm6.35 1.59c0-.73.32-1.3.97-1.71.64-.4 1.67-.68 3.08-.84 0-.17-.02-.34-.07-.51-.05-.16-.12-.3-.22-.43s-.22-.22-.38-.3c-.15-.06-.34-.1-.58-.1-.34 0-.68.07-1 .2s-.63.29-.93.47l-.59-1.08c.39-.24.81-.45 1.28-.63.47-.17.99-.26 1.54-.26.86 0 1.51.25 1.93.76s.63 1.25.63 2.21v4.07h-1.32l-.12-.76h-.05c-.3.27-.63.48-.98.66s-.73.27-1.14.27c-.61 0-1.1-.19-1.48-.56-.38-.36-.57-.85-.57-1.46zm1.57-.12c0 .3.09.53.27.67.19.14.42.21.71.21.28 0 .54-.07.77-.2s.48-.31.73-.56v-1.54c-.47.06-.86.13-1.18.23-.31.09-.57.19-.76.31s-.33.25-.41.4c-.09.15-.13.31-.13.48zm6.29-3.63h-.98v-1.2l1.06-.07.2-1.88h1.34v1.88h1.75v1.27h-1.75v3.28c0 .8.32 1.2.97 1.2.12 0 .24-.01.37-.04.12-.03.24-.07.34-.11l.28 1.19c-.19.06-.4.12-.64.17-.23.05-.49.08-.76.08-.4 0-.74-.06-1.02-.18-.27-.13-.49-.3-.67-.52-.17-.21-.3-.48-.37-.78-.08-.3-.12-.64-.12-1.01zm4.36 2.17c0-.56.09-1.06.27-1.51s.41-.83.71-1.14c.29-.3.63-.54 1.01-.71.39-.17.78-.25 1.18-.25.47 0 .88.08 1.23.24.36.16.65.38.89.67s.42.63.54 1.03c.12.41.18.84.18 1.32 0 .32-.02.57-.07.76h-4.37c.08.62.29 1.1.65 1.44.36.33.82.5 1.38.5.3 0 .58-.04.84-.13.25-.09.51-.21.76-.37l.54 1.01c-.32.21-.69.39-1.09.53s-.82.21-1.26.21c-.47 0-.92-.08-1.33-.25-.41-.16-.77-.4-1.08-.7-.3-.31-.54-.69-.72-1.13-.17-.44-.26-.95-.26-1.52zm4.61-.62c0-.55-.11-.98-.34-1.28-.23-.31-.58-.47-1.06-.47-.41 0-.77.15-1.08.45-.31.29-.5.73-.57 1.3zm3.01 2.23c.31.24.61.43.92.57.3.13.63.2.98.2.38 0 .65-.08.83-.23s.27-.35.27-.6c0-.14-.05-.26-.13-.37-.08-.1-.2-.2-.34-.28-.14-.09-.29-.16-.47-.23l-.53-.22c-.23-.09-.46-.18-.69-.3-.23-.11-.44-.24-.62-.4s-.33-.35-.45-.55c-.12-.21-.18-.46-.18-.75 0-.61.23-1.1.68-1.49.44-.38 1.06-.57 1.83-.57.48 0 .91.08 1.29.25s.71.36.99.57l-.74.98c-.24-.17-.49-.32-.73-.42-.25-.11-.51-.16-.78-.16-.35 0-.6.07-.76.21-.17.15-.25.33-.25.54 0 .14.04.26.12.36s.18.18.31.26c.14.07.29.14.46.21l.54.19c.23.09.47.18.7.29s.44.24.64.4c.19.16.34.35.46.58.11.23.17.5.17.82 0 .3-.06.58-.17.83-.12.26-.29.48-.51.68-.23.19-.51.34-.84.45-.34.11-.72.17-1.15.17-.48 0-.95-.09-1.41-.27-.46-.19-.86-.41-1.2-.68z" fill="#535353"/></g></svg>"></a></div><div class="c-bibliographic-information__column"><h3 class="c-article__sub-heading" id="citeas">Cite this article</h3><p class="c-bibliographic-information__citation">Grochala, W. On the position of helium and neon in the Periodic Table of Elements. <i>Found Chem</i> <b>20</b>, 191–207 (2018). https://doi.org/10.1007/s10698-017-9302-7</p><p class="c-bibliographic-information__download-citation u-hide-print"><a data-test="citation-link" data-track="click" data-track-action="download article citation" data-track-label="link" data-track-external="" rel="nofollow" href="https://citation-needed.springer.com/v2/references/10.1007/s10698-017-9302-7?format=refman&flavour=citation">Download citation<svg width="16" height="16" focusable="false" role="img" aria-hidden="true" class="u-icon"><use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-eds-i-download-medium"></use></svg></a></p><ul class="c-bibliographic-information__list" data-test="publication-history"><li class="c-bibliographic-information__list-item"><p>Published<span class="u-hide">: </span><span class="c-bibliographic-information__value"><time datetime="2017-11-01">01 November 2017</time></span></p></li><li class="c-bibliographic-information__list-item"><p>Issue Date<span class="u-hide">: </span><span class="c-bibliographic-information__value"><time datetime="2018-10">October 2018</time></span></p></li><li class="c-bibliographic-information__list-item c-bibliographic-information__list-item--full-width"><p><abbr title="Digital Object Identifier">DOI</abbr><span class="u-hide">: </span><span class="c-bibliographic-information__value">https://doi.org/10.1007/s10698-017-9302-7</span></p></li></ul><div data-component="share-box"><div class="c-article-share-box u-display-none" hidden=""><h3 class="c-article__sub-heading">Share this article</h3><p class="c-article-share-box__description">Anyone you share the following link with will be able to read this content:</p><button class="js-get-share-url c-article-share-box__button" type="button" id="get-share-url" data-track="click" data-track-label="button" data-track-external="" data-track-action="get shareable link">Get shareable link</button><div class="js-no-share-url-container u-display-none" hidden=""><p class="js-c-article-share-box__no-sharelink-info c-article-share-box__no-sharelink-info">Sorry, a shareable link is not currently available for this article.</p></div><div class="js-share-url-container u-display-none" hidden=""><p class="js-share-url c-article-share-box__only-read-input" id="share-url" data-track="click" data-track-label="button" data-track-action="select share url"></p><button class="js-copy-share-url c-article-share-box__button--link-like" type="button" id="copy-share-url" data-track="click" data-track-label="button" data-track-action="copy share url" data-track-external="">Copy to clipboard</button></div><p class="js-c-article-share-box__additional-info c-article-share-box__additional-info"> Provided by the Springer Nature SharedIt content-sharing initiative </p></div></div><h3 class="c-article__sub-heading">Keywords</h3><ul class="c-article-subject-list"><li class="c-article-subject-list__subject"><span><a href="/search?query=Periodic%20Table&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Periodic Table</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Hydrogen&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Hydrogen</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Fluorine&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Fluorine</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Beryllium&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Beryllium</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Noble%20gases&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Noble gases</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Helium&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Helium</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Neon&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Neon</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Argon&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Argon</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Reactivity&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Reactivity</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Electronic%20structure&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Electronic structure</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Ionization%20potential&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Ionization potential</a></span></li><li class="c-article-subject-list__subject"><span><a href="/search?query=Electron%20affinity&facet-discipline="Philosophy"" data-track="click" data-track-action="view keyword" data-track-label="link">Electron affinity</a></span></li></ul><div data-component="article-info-list"></div></div></div></div></div></section> </div> </main> <div class="c-article-sidebar u-text-sm u-hide-print l-with-sidebar__sidebar" id="sidebar" data-container-type="reading-companion" data-track-component="reading companion"> <aside> <div class="app-card-service" data-test="article-checklist-banner"> <div> <a class="app-card-service__link" data-track="click_presubmission_checklist" data-track-context="article page top of reading companion" data-track-category="pre-submission-checklist" data-track-action="clicked article page checklist banner test 2 old version" data-track-label="link" href="https://beta.springernature.com/pre-submission?journalId=10698" data-test="article-checklist-banner-link"> <span class="app-card-service__link-text">Use our pre-submission checklist</span> <svg class="app-card-service__link-icon" aria-hidden="true" focusable="false"><use xlink:href="#icon-eds-i-arrow-right-small"></use></svg> </a> <p class="app-card-service__description">Avoid common mistakes on your manuscript.</p> </div> <div class="app-card-service__icon-container"> <svg class="app-card-service__icon" aria-hidden="true" focusable="false"> <use xlink:href="#icon-eds-i-clipboard-check-medium"></use> </svg> </div> </div> <div data-test="collections"> </div> <div data-test="editorial-summary"> </div> <div class="c-reading-companion"> <div class="c-reading-companion__sticky" data-component="reading-companion-sticky" data-test="reading-companion-sticky"> <div class="c-reading-companion__panel c-reading-companion__sections c-reading-companion__panel--active" id="tabpanel-sections"> <div class="u-lazy-ad-wrapper u-mt-16 u-hide" data-component-mpu><div class="c-ad c-ad--300x250"> <div class="c-ad__inner"> <p class="c-ad__label">Advertisement</p> <div id="div-gpt-ad-MPU1" class="div-gpt-ad grade-c-hide" data-pa11y-ignore data-gpt data-gpt-unitpath="/270604982/springerlink/10698/article" data-gpt-sizes="300x250" data-test="MPU1-ad" data-gpt-targeting="pos=MPU1;articleid=s10698-017-9302-7;"> </div> </div> </div> </div> </div> <div class="c-reading-companion__panel c-reading-companion__figures c-reading-companion__panel--full-width" id="tabpanel-figures"></div> <div class="c-reading-companion__panel c-reading-companion__references c-reading-companion__panel--full-width" id="tabpanel-references"></div> </div> </div> </aside> </div> </div> </article> <div class="app-elements"> <div class="eds-c-header__expander eds-c-header__expander--search" id="eds-c-header-popup-search"> <h2 class="eds-c-header__heading">Search</h2> <div class="u-container"> <search class="eds-c-header__search" role="search" aria-label="Search from the header"> <form method="GET" action="//link.springer.com/search" data-test="header-search" data-track="search" data-track-context="search from header" data-track-action="submit search form" data-track-category="unified header" data-track-label="form" > <label for="eds-c-header-search" class="eds-c-header__search-label">Search by keyword or author</label> <div class="eds-c-header__search-container"> <input id="eds-c-header-search" class="eds-c-header__search-input" autocomplete="off" name="query" type="search" value="" required> <button class="eds-c-header__search-button" type="submit"> <svg class="eds-c-header__icon" aria-hidden="true" focusable="false"> <use xlink:href="#icon-eds-i-search-medium"></use> </svg> <span class="u-visually-hidden">Search</span> </button> </div> </form> </search> </div> </div> <div class="eds-c-header__expander eds-c-header__expander--menu" id="eds-c-header-nav"> <h2 class="eds-c-header__heading">Navigation</h2> <ul class="eds-c-header__list"> <li class="eds-c-header__list-item"> <a class="eds-c-header__link" href="https://link.springer.com/journals/" data-track="nav_find_a_journal" data-track-context="unified header" data-track-action="click find a journal" data-track-category="unified header" data-track-label="link" > Find a journal </a> </li> <li class="eds-c-header__list-item"> <a class="eds-c-header__link" href="https://www.springernature.com/gp/authors" data-track="nav_how_to_publish" data-track-context="unified header" data-track-action="click publish with us link" data-track-category="unified header" data-track-label="link" > Publish with us </a> </li> <li class="eds-c-header__list-item"> <a class="eds-c-header__link" href="https://link.springernature.com/home/" data-track="nav_track_your_research" data-track-context="unified header" data-track-action="click track your research" data-track-category="unified header" data-track-label="link" > Track your research </a> </li> </ul> </div> <footer > <div class="eds-c-footer" > <div class="eds-c-footer__container"> <div class="eds-c-footer__grid eds-c-footer__group--separator"> <div class="eds-c-footer__group"> <h3 class="eds-c-footer__heading">Discover content</h3> <ul class="eds-c-footer__list"> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://link.springer.com/journals/a/1" data-track="nav_journals_a_z" data-track-action="journals a-z" data-track-context="unified footer" data-track-label="link">Journals A-Z</a></li> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://link.springer.com/books/a/1" data-track="nav_books_a_z" data-track-action="books a-z" data-track-context="unified footer" data-track-label="link">Books A-Z</a></li> </ul> </div> <div class="eds-c-footer__group"> <h3 class="eds-c-footer__heading">Publish with us</h3> <ul class="eds-c-footer__list"> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://link.springer.com/journals" data-track="nav_journal_finder" data-track-action="journal finder" data-track-context="unified footer" data-track-label="link">Journal finder</a></li> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.springernature.com/gp/authors" data-track="nav_publish_your_research" data-track-action="publish your research" data-track-context="unified footer" data-track-label="link">Publish your research</a></li> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.springernature.com/gp/open-research/about/the-fundamentals-of-open-access-and-open-research" data-track="nav_open_access_publishing" data-track-action="open access publishing" data-track-context="unified footer" data-track-label="link">Open access publishing</a></li> </ul> </div> <div class="eds-c-footer__group"> <h3 class="eds-c-footer__heading">Products and services</h3> <ul class="eds-c-footer__list"> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.springernature.com/gp/products" data-track="nav_our_products" data-track-action="our products" data-track-context="unified footer" data-track-label="link">Our products</a></li> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.springernature.com/gp/librarians" data-track="nav_librarians" data-track-action="librarians" data-track-context="unified footer" data-track-label="link">Librarians</a></li> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.springernature.com/gp/societies" data-track="nav_societies" data-track-action="societies" data-track-context="unified footer" data-track-label="link">Societies</a></li> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.springernature.com/gp/partners" data-track="nav_partners_and_advertisers" data-track-action="partners and advertisers" data-track-context="unified footer" data-track-label="link">Partners and advertisers</a></li> </ul> </div> <div class="eds-c-footer__group"> <h3 class="eds-c-footer__heading">Our imprints</h3> <ul class="eds-c-footer__list"> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.springer.com/" data-track="nav_imprint_Springer" data-track-action="Springer" data-track-context="unified footer" data-track-label="link">Springer</a></li> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.nature.com/" data-track="nav_imprint_Nature_Portfolio" data-track-action="Nature Portfolio" data-track-context="unified footer" data-track-label="link">Nature Portfolio</a></li> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.biomedcentral.com/" data-track="nav_imprint_BMC" data-track-action="BMC" data-track-context="unified footer" data-track-label="link">BMC</a></li> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.palgrave.com/" data-track="nav_imprint_Palgrave_Macmillan" data-track-action="Palgrave Macmillan" data-track-context="unified footer" data-track-label="link">Palgrave Macmillan</a></li> <li class="eds-c-footer__item"><a class="eds-c-footer__link" href="https://www.apress.com/" data-track="nav_imprint_Apress" data-track-action="Apress" data-track-context="unified footer" data-track-label="link">Apress</a></li> </ul> </div> </div> </div> <div class="eds-c-footer__container"> <nav aria-label="footer navigation"> <ul class="eds-c-footer__links"> <li class="eds-c-footer__item"> <button class="eds-c-footer__link" data-cc-action="preferences" data-track="dialog_manage_cookies" data-track-action="Manage cookies" data-track-context="unified footer" data-track-label="link"><span class="eds-c-footer__button-text">Your privacy choices/Manage cookies</span></button> </li> <li class="eds-c-footer__item"> <a class="eds-c-footer__link" href="https://www.springernature.com/gp/legal/ccpa" data-track="nav_california_privacy_statement" data-track-action="california privacy statement" data-track-context="unified footer" data-track-label="link">Your US state privacy rights</a> </li> <li class="eds-c-footer__item"> <a class="eds-c-footer__link" href="https://www.springernature.com/gp/info/accessibility" data-track="nav_accessibility_statement" data-track-action="accessibility statement" data-track-context="unified footer" data-track-label="link">Accessibility statement</a> </li> <li class="eds-c-footer__item"> <a class="eds-c-footer__link" href="https://link.springer.com/termsandconditions" data-track="nav_terms_and_conditions" data-track-action="terms and conditions" data-track-context="unified footer" data-track-label="link">Terms and conditions</a> </li> <li class="eds-c-footer__item"> <a class="eds-c-footer__link" href="https://link.springer.com/privacystatement" data-track="nav_privacy_policy" data-track-action="privacy policy" data-track-context="unified footer" data-track-label="link">Privacy policy</a> </li> <li class="eds-c-footer__item"> <a class="eds-c-footer__link" href="https://support.springernature.com/en/support/home" data-track="nav_help_and_support" data-track-action="help and support" data-track-context="unified footer" data-track-label="link">Help and support</a> </li> <li class="eds-c-footer__item"> <a class="eds-c-footer__link" href="https://support.springernature.com/en/support/solutions/articles/6000255911-subscription-cancellations" data-track-action="cancel contracts here">Cancel contracts here</a> </li> </ul> </nav> <div class="eds-c-footer__user"> <p class="eds-c-footer__user-info"> <span data-test="footer-user-ip">8.222.208.146</span> </p> <p class="eds-c-footer__user-info" data-test="footer-business-partners">Not affiliated</p> </div> <a href="https://www.springernature.com/" class="eds-c-footer__link"> <img src="/oscar-static/images/logo-springernature-white-19dd4ba190.svg" alt="Springer Nature" loading="lazy" width="200" height="20"/> </a> <p class="eds-c-footer__legal" data-test="copyright">© 2024 Springer Nature</p> </div> </div> </footer> </div> </body> </html>