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class="vector-toc-numb">5</span> <span>Further reading</span> </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon 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Available in 58 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-58" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">58 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-anp mw-list-item"><a href="https://anp.wikipedia.org/wiki/%E0%A4%86%E0%A4%B5%E0%A4%B0%E0%A5%8D%E0%A4%A4_1_%E0%A4%A4%E0%A4%A4%E0%A5%8D%E0%A4%B5" title="आवर्त 1 तत्व – Angika" lang="anp" hreflang="anp" data-title="आवर्त 1 तत्व" data-language-autonym="अंगिका" data-language-local-name="Angika" class="interlanguage-link-target"><span>अंगिका</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%B9%D9%86%D8%A7%D8%B5%D8%B1_%D8%A7%D9%84%D8%AF%D9%88%D8%B1%D8%A9_%D8%A7%D9%84%D8%A3%D9%88%D9%84%D9%89" title="عناصر الدورة الأولى – Arabic" lang="ar" hreflang="ar" data-title="عناصر الدورة الأولى" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-an mw-list-item"><a href="https://an.wikipedia.org/wiki/Elementos_d%27o_periodo_1" title="Elementos d'o periodo 1 – Aragonese" lang="an" hreflang="an" data-title="Elementos d'o periodo 1" data-language-autonym="Aragonés" data-language-local-name="Aragonese" class="interlanguage-link-target"><span>Aragonés</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Elementos_del_periodu_1" title="Elementos del periodu 1 – Asturian" lang="ast" hreflang="ast" data-title="Elementos del periodu 1" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/D%C3%B6vri_sistemin_birinci_periodu" title="Dövri sistemin birinci periodu – Azerbaijani" lang="az" hreflang="az" data-title="Dövri sistemin birinci periodu" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AA%E0%A7%8D%E0%A6%B0%E0%A6%A5%E0%A6%AE_%E0%A6%AA%E0%A6%B0%E0%A7%8D%E0%A6%AF%E0%A6%BE%E0%A6%AF%E0%A6%BC%E0%A7%87%E0%A6%B0_%E0%A6%AE%E0%A7%8C%E0%A6%B2" title="প্রথম পর্যায়ের মৌল – Bangla" lang="bn" hreflang="bn" data-title="প্রথম পর্যায়ের মৌল" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-zh-min-nan mw-list-item"><a href="https://zh-min-nan.wikipedia.org/wiki/T%C4%93-1_chiu-k%C3%AE_go%C3%A2n-s%C3%B2%CD%98" title="Tē-1 chiu-kî goân-sò͘ – Minnan" lang="nan" hreflang="nan" data-title="Tē-1 chiu-kî goân-sò͘" data-language-autonym="閩南語 / Bân-lâm-gú" data-language-local-name="Minnan" class="interlanguage-link-target"><span>閩南語 / Bân-lâm-gú</span></a></li><li class="interlanguage-link interwiki-ba mw-list-item"><a href="https://ba.wikipedia.org/wiki/%D0%9F%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D0%B8%D0%BA_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0%D0%BD%D1%8B%D2%A3_%D0%B1%D0%B5%D1%80%D0%B5%D0%BD%D1%81%D0%B5_%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D1%8B" title="Периодик системаның беренсе периоды – Bashkir" lang="ba" hreflang="ba" data-title="Периодик системаның беренсе периоды" data-language-autonym="Башҡортса" data-language-local-name="Bashkir" class="interlanguage-link-target"><span>Башҡортса</span></a></li><li class="interlanguage-link interwiki-bh mw-list-item"><a href="https://bh.wikipedia.org/wiki/%E0%A4%AA%E0%A5%80%E0%A4%B0%E0%A4%BF%E0%A4%AF%E0%A4%A1_1_%E0%A4%A4%E0%A4%A4%E0%A5%8D%E0%A4%B5" title="पीरियड 1 तत्व – Bhojpuri" lang="bh" hreflang="bh" data-title="पीरियड 1 तत्व" data-language-autonym="भोजपुरी" data-language-local-name="Bhojpuri" class="interlanguage-link-target"><span>भोजपुरी</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%9F%D0%B5%D1%80%D0%B8%D0%BE%D0%B4_1_%D0%BD%D0%B0_%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D0%B8%D1%87%D0%BD%D0%B0%D1%82%D0%B0_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0" title="Период 1 на периодичната система – Bulgarian" lang="bg" hreflang="bg" data-title="Период 1 на периодичната система" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-ca badge-Q17437798 badge-goodarticle mw-list-item" title="good article badge"><a href="https://ca.wikipedia.org/wiki/Elements_del_per%C3%ADode_1" title="Elements del període 1 – Catalan" lang="ca" hreflang="ca" data-title="Elements del període 1" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/1._perioda" title="1. perioda – Czech" lang="cs" hreflang="cs" data-title="1. perioda" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-cy mw-list-item"><a href="https://cy.wikipedia.org/wiki/Elfen_cyfnod_1" title="Elfen cyfnod 1 – Welsh" lang="cy" hreflang="cy" data-title="Elfen cyfnod 1" data-language-autonym="Cymraeg" data-language-local-name="Welsh" class="interlanguage-link-target"><span>Cymraeg</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Periode_1-grundstof" title="Periode 1-grundstof – Danish" lang="da" hreflang="da" data-title="Periode 1-grundstof" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Chemische_Elemente_der_ersten_Periode" title="Chemische Elemente der ersten Periode – German" lang="de" hreflang="de" data-title="Chemische Elemente der ersten Periode" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%A3%CF%84%CE%BF%CE%B9%CF%87%CE%B5%CE%AF%CE%BF_%CE%A0%CE%B5%CF%81%CE%B9%CF%8C%CE%B4%CE%BF%CF%85_1" title="Στοιχείο Περιόδου 1 – Greek" lang="el" hreflang="el" data-title="Στοιχείο Περιόδου 1" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es badge-Q17437798 badge-goodarticle mw-list-item" title="good article badge"><a href="https://es.wikipedia.org/wiki/Elementos_del_periodo_1" title="Elementos del periodo 1 – Spanish" lang="es" hreflang="es" data-title="Elementos del periodo 1" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Elemento_de_periodo_1" title="Elemento de periodo 1 – Esperanto" lang="eo" hreflang="eo" data-title="Elemento de periodo 1" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/1._periodoko_elementu" title="1. periodoko elementu – Basque" lang="eu" hreflang="eu" data-title="1. periodoko elementu" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa badge-Q17437798 badge-goodarticle mw-list-item" title="good article badge"><a href="https://fa.wikipedia.org/wiki/%D8%AF%D9%88%D8%B1%D9%87_%DB%B1_%D8%AC%D8%AF%D9%88%D9%84_%D8%AA%D9%86%D8%A7%D9%88%D8%A8%DB%8C" title="دوره ۱ جدول تناوبی – Persian" lang="fa" hreflang="fa" data-title="دوره ۱ جدول تناوبی" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/P%C3%A9riode_1_du_tableau_p%C3%A9riodique" title="Période 1 du tableau périodique – French" lang="fr" hreflang="fr" data-title="Période 1 du tableau périodique" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-fy mw-list-item"><a href="https://fy.wikipedia.org/wiki/Perioade_1_(periodyk_systeem)" title="Perioade 1 (periodyk systeem) – Western Frisian" lang="fy" hreflang="fy" data-title="Perioade 1 (periodyk systeem)" data-language-autonym="Frysk" data-language-local-name="Western Frisian" class="interlanguage-link-target"><span>Frysk</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/1%EC%A3%BC%EA%B8%B0_%EC%9B%90%EC%86%8C" title="1주기 원소 – Korean" lang="ko" hreflang="ko" data-title="1주기 원소" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-id badge-Q17437798 badge-goodarticle mw-list-item" title="good article badge"><a href="https://id.wikipedia.org/wiki/Unsur_periode_1" title="Unsur periode 1 – Indonesian" lang="id" hreflang="id" data-title="Unsur periode 1" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-ia mw-list-item"><a href="https://ia.wikipedia.org/wiki/Elementos_de_periodo_1" title="Elementos de periodo 1 – Interlingua" lang="ia" hreflang="ia" data-title="Elementos de periodo 1" data-language-autonym="Interlingua" data-language-local-name="Interlingua" class="interlanguage-link-target"><span>Interlingua</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Elementi_del_periodo_1" title="Elementi del periodo 1 – Italian" lang="it" hreflang="it" data-title="Elementi del periodo 1" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%94%E1%83%9A%E1%83%94%E1%83%9B%E1%83%94%E1%83%9C%E1%83%A2%E1%83%97%E1%83%90_%E1%83%9E%E1%83%94%E1%83%A0%E1%83%98%E1%83%9D%E1%83%93%E1%83%A3%E1%83%9A%E1%83%98_%E1%83%A1%E1%83%98%E1%83%A1%E1%83%A2%E1%83%94%E1%83%9B%E1%83%98%E1%83%A1_%E1%83%9E%E1%83%98%E1%83%A0%E1%83%95%E1%83%94%E1%83%9A%E1%83%98_%E1%83%9E%E1%83%94%E1%83%A0%E1%83%98%E1%83%9D%E1%83%93%E1%83%98" title="ელემენტთა პერიოდული სისტემის პირველი პერიოდი – Georgian" lang="ka" hreflang="ka" data-title="ელემენტთა პერიოდული სისტემის პირველი პერიოდი" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Elementum_periodi_primae" title="Elementum periodi primae – Latin" lang="la" hreflang="la" data-title="Elementum periodi primae" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Pirmojo_periodo_elementas" title="Pirmojo periodo elementas – Lithuanian" lang="lt" hreflang="lt" data-title="Pirmojo periodo elementas" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-lmo mw-list-item"><a href="https://lmo.wikipedia.org/wiki/Element_del_period_1" title="Element del period 1 – Lombard" lang="lmo" hreflang="lmo" data-title="Element del period 1" data-language-autonym="Lombard" data-language-local-name="Lombard" class="interlanguage-link-target"><span>Lombard</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/I_%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D0%B0_%D0%BD%D0%B0_%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D0%BD%D0%B8%D0%BE%D1%82_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC" title="I периода на периодниот систем – Macedonian" lang="mk" hreflang="mk" data-title="I периода на периодниот систем" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%92%E0%B4%A8%E0%B5%8D%E0%B4%A8%E0%B4%BE%E0%B4%82_%E0%B4%AA%E0%B5%80%E0%B4%B0%E0%B5%80%E0%B4%A1%E0%B5%8D_%E0%B4%AE%E0%B5%82%E0%B4%B2%E0%B4%95%E0%B4%99%E0%B5%8D%E0%B4%99%E0%B5%BE" title="ഒന്നാം പീരീഡ് മൂലകങ്ങൾ – Malayalam" lang="ml" hreflang="ml" data-title="ഒന്നാം പീരീഡ് മൂലകങ്ങൾ" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Unsur_kala_1" title="Unsur kala 1 – Malay" lang="ms" hreflang="ms" data-title="Unsur kala 1" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Periode-1-element" title="Periode-1-element – Dutch" lang="nl" hreflang="nl" data-title="Periode-1-element" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E7%AC%AC1%E5%91%A8%E6%9C%9F%E5%85%83%E7%B4%A0" title="第1周期元素 – Japanese" lang="ja" hreflang="ja" data-title="第1周期元素" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-frr mw-list-item"><a href="https://frr.wikipedia.org/wiki/Periode-1-Element" title="Periode-1-Element – Northern Frisian" lang="frr" hreflang="frr" data-title="Periode-1-Element" data-language-autonym="Nordfriisk" data-language-local-name="Northern Frisian" class="interlanguage-link-target"><span>Nordfriisk</span></a></li><li class="interlanguage-link interwiki-pa mw-list-item"><a href="https://pa.wikipedia.org/wiki/%E0%A8%AA%E0%A9%80%E0%A8%B0%E0%A8%A1_1_%E0%A8%A4%E0%A9%B1%E0%A8%A4" title="ਪੀਰਡ 1 ਤੱਤ – Punjabi" lang="pa" hreflang="pa" data-title="ਪੀਰਡ 1 ਤੱਤ" data-language-autonym="ਪੰਜਾਬੀ" data-language-local-name="Punjabi" class="interlanguage-link-target"><span>ਪੰਜਾਬੀ</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Pierwiastki_pierwszego_okresu" title="Pierwiastki pierwszego okresu – Polish" lang="pl" hreflang="pl" data-title="Pierwiastki pierwszego okresu" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Per%C3%ADodo_1_(qu%C3%ADmica)" title="Período 1 (química) – Portuguese" lang="pt" hreflang="pt" data-title="Período 1 (química)" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Elementele_perioadei_1" title="Elementele perioadei 1 – Romanian" lang="ro" hreflang="ro" data-title="Elementele perioadei 1" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%9F%D0%B5%D1%80%D0%B2%D1%8B%D0%B9_%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4_%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0%BE%D0%B9_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D1%8B" title="Первый период периодической системы – Russian" lang="ru" hreflang="ru" data-title="Первый период периодической системы" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-si mw-list-item"><a href="https://si.wikipedia.org/wiki/1_%E0%B7%80%E0%B6%B1_%E0%B6%86%E0%B7%80%E0%B6%BB%E0%B7%8A%E0%B6%AD%E0%B6%BA%E0%B7%9A_%E0%B6%B8%E0%B7%96%E0%B6%BD%E0%B6%AF%E0%B7%8A%E2%80%8D%E0%B6%BB%E0%B7%80%E0%B7%8A%E2%80%8D%E0%B6%BA%E0%B6%BA" title="1 වන ආවර්තයේ මූලද්‍රව්‍යය – Sinhala" lang="si" hreflang="si" data-title="1 වන ආවර්තයේ මූලද්‍රව්‍යය" data-language-autonym="සිංහල" data-language-local-name="Sinhala" class="interlanguage-link-target"><span>සිංහල</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Period_1_element" title="Period 1 element – Simple English" lang="en-simple" hreflang="en-simple" data-title="Period 1 element" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/1._peri%C3%B3da" title="1. perióda – Slovak" lang="sk" hreflang="sk" data-title="1. perióda" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Element_1._periode" title="Element 1. periode – Slovenian" lang="sl" hreflang="sl" data-title="Element 1. periode" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/1._%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D0%B0_%D1%85%D0%B5%D0%BC%D0%B8%D1%98%D1%81%D0%BA%D0%B8%D1%85_%D0%B5%D0%BB%D0%B5%D0%BC%D0%B5%D0%BD%D0%B0%D1%82%D0%B0" title="1. периода хемијских елемената – Serbian" lang="sr" hreflang="sr" data-title="1. периода хемијских елемената" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Elementi_1._periode" title="Elementi 1. periode – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Elementi 1. periode" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Jakson_1_alkuaine" title="Jakson 1 alkuaine – Finnish" lang="fi" hreflang="fi" data-title="Jakson 1 alkuaine" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%95%E0%AE%BF%E0%AE%9F%E0%AF%88%E0%AE%95%E0%AF%8D%E0%AE%95%E0%AF%81%E0%AE%B4%E0%AF%81_1_%E0%AE%A4%E0%AE%A9%E0%AE%BF%E0%AE%AE%E0%AE%99%E0%AF%8D%E0%AE%95%E0%AE%B3%E0%AF%8D" title="கிடைக்குழு 1 தனிமங்கள் – Tamil" lang="ta" hreflang="ta" data-title="கிடைக்குழு 1 தனிமங்கள்" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-te mw-list-item"><a href="https://te.wikipedia.org/wiki/%E0%B0%AA%E0%B1%80%E0%B0%B0%E0%B0%BF%E0%B0%AF%E0%B0%A1%E0%B1%8D_1_%E0%B0%AE%E0%B1%82%E0%B0%B2%E0%B0%95%E0%B0%82" title="పీరియడ్ 1 మూలకం – Telugu" lang="te" hreflang="te" data-title="పీరియడ్ 1 మూలకం" data-language-autonym="తెలుగు" data-language-local-name="Telugu" class="interlanguage-link-target"><span>తెలుగు</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%98%E0%B8%B2%E0%B8%95%E0%B8%B8%E0%B8%84%E0%B8%B2%E0%B8%9A_1" title="ธาตุคาบ 1 – Thai" lang="th" hreflang="th" data-title="ธาตุคาบ 1" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/1._periyot_elementi" title="1. periyot elementi – Turkish" lang="tr" hreflang="tr" data-title="1. periyot elementi" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%9F%D0%B5%D1%80%D1%96%D0%BE%D0%B4_1_%D0%BF%D0%B5%D1%80%D1%96%D0%BE%D0%B4%D0%B8%D1%87%D0%BD%D0%BE%D1%97_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B8_%D0%B5%D0%BB%D0%B5%D0%BC%D0%B5%D0%BD%D1%82%D1%96%D0%B2" title="Період 1 періодичної системи елементів – Ukrainian" lang="uk" hreflang="uk" data-title="Період 1 періодичної системи елементів" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Nguy%C3%AAn_t%E1%BB%91_chu_k%E1%BB%B3_1" title="Nguyên tố chu kỳ 1 – Vietnamese" lang="vi" hreflang="vi" data-title="Nguyên tố chu kỳ 1" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-vls mw-list-item"><a href="https://vls.wikipedia.org/wiki/Periode-1-element" title="Periode-1-element – West Flemish" lang="vls" hreflang="vls" data-title="Periode-1-element" data-language-autonym="West-Vlams" data-language-local-name="West Flemish" class="interlanguage-link-target"><span>West-Vlams</span></a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%E7%AC%AC1%E5%91%A8%E6%9C%9F%E5%85%83%E7%B4%A0" title="第1周期元素 – Wu" lang="wuu" hreflang="wuu" data-title="第1周期元素" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target"><span>吴语</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E7%AC%AC1%E9%80%B1%E6%9C%9F%E5%85%83%E7%B4%A0" title="第1週期元素 – Cantonese" lang="yue" hreflang="yue" data-title="第1週期元素" data-language-autonym="粵語" data-language-local-name="Cantonese" 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Click here for more information."><img alt="This is a good article. Click here for more information." src="//upload.wikimedia.org/wikipedia/en/thumb/9/94/Symbol_support_vote.svg/19px-Symbol_support_vote.svg.png" decoding="async" width="19" height="20" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/94/Symbol_support_vote.svg/29px-Symbol_support_vote.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/94/Symbol_support_vote.svg/39px-Symbol_support_vote.svg.png 2x" data-file-width="180" data-file-height="185" /></a></span></div></div> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Element in first row of periodic table</div> <div role="navigation" aria-labelledby="micro-periodic-table-title" style="float:right; background:#f8f8f8; padding:0.3em; border:1px solid #a9a9a9; margin:0 0 0.25em 0.5em; text-align:center;;"> <div id="micro-periodic-table-title" style="background:#d8d8d8; padding:0.15em 0.3em; font-size:90%; line-height:110%; font-weight:bold;">Period 1 in the <a href="/wiki/Periodic_table" title="Periodic table">periodic table</a></div> <div style="margin: 0.15em 0; display:table-row;"><div style="background-color:transparent; color:inherit; margin:0; padding:0; text-align:center; border:none;"> <table style="empty-cells:hidden; border:none; padding:0; border-spacing:1px; border-collapse:separate; margin:0;"> <tbody><tr> <td style="border:none;padding:0;"><a href="/wiki/Hydrogen" title="Hydrogen"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999; border:1px solid black; box-sizing: border-box;;">Hydrogen</span></a> </td> <td colspan="30" style="border:none;padding:0;"> </td> <td style="border:none;padding:0;"><a href="/wiki/Helium" title="Helium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999; border:1px solid black; box-sizing: border-box;;">Helium</span></a> </td></tr> <tr> <td style="border:none;padding:0;"><a href="/wiki/Lithium" title="Lithium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Lithium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Beryllium" title="Beryllium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Beryllium</span></a> </td> <td colspan="24" style="border:none;padding:0;"> </td> <td style="border:none;padding:0;"><a href="/wiki/Boron" title="Boron"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Boron</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Carbon" title="Carbon"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Carbon</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Nitrogen" title="Nitrogen"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Nitrogen</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Oxygen" title="Oxygen"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Oxygen</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Fluorine" title="Fluorine"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Fluorine</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Neon" title="Neon"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Neon</span></a> </td></tr> <tr> <td style="border:none;padding:0;"><a href="/wiki/Sodium" title="Sodium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Sodium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Magnesium" title="Magnesium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Magnesium</span></a> </td> <td colspan="24" style="border:none;padding:0;"> </td> <td style="border:none;padding:0;"><a href="/wiki/Aluminium" title="Aluminium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Aluminium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Silicon" title="Silicon"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Silicon</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Phosphorus" title="Phosphorus"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Phosphorus</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Sulfur" title="Sulfur"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Sulfur</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Chlorine" title="Chlorine"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Chlorine</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Argon" title="Argon"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Argon</span></a> </td></tr> <tr> <td style="border:none;padding:0;"><a href="/wiki/Potassium" title="Potassium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Potassium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Calcium" title="Calcium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Calcium</span></a> </td> <td colspan="14" style="border:none;padding:0;"> </td> <td style="border:none;padding:0;"><a href="/wiki/Scandium" title="Scandium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Scandium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Titanium" title="Titanium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Titanium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Vanadium" title="Vanadium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Vanadium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Chromium" title="Chromium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Chromium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Manganese" title="Manganese"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Manganese</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Iron" title="Iron"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Iron</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Cobalt" title="Cobalt"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Cobalt</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Nickel" title="Nickel"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Nickel</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Copper" title="Copper"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Copper</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Zinc" title="Zinc"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Zinc</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Gallium" title="Gallium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Gallium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Germanium" title="Germanium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Germanium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Arsenic" title="Arsenic"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Arsenic</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Selenium" title="Selenium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Selenium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Bromine" title="Bromine"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Bromine</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Krypton" title="Krypton"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Krypton</span></a> </td></tr> <tr> <td style="border:none;padding:0;"><a href="/wiki/Rubidium" title="Rubidium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Rubidium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Strontium" title="Strontium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Strontium</span></a> </td> <td style="border:none;padding:0;; width:0;"> </td> <td colspan="13" style="border:none;padding:0;"> </td> <td style="border:none;padding:0;"><a href="/wiki/Yttrium" title="Yttrium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Yttrium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Zirconium" title="Zirconium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Zirconium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Niobium" title="Niobium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Niobium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Molybdenum" title="Molybdenum"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Molybdenum</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Technetium" title="Technetium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Technetium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Ruthenium" title="Ruthenium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Ruthenium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Rhodium" title="Rhodium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Rhodium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Palladium" title="Palladium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Palladium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Silver" title="Silver"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Silver</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Cadmium" title="Cadmium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Cadmium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Indium" title="Indium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Indium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Tin" title="Tin"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Tin</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Antimony" title="Antimony"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Antimony</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Tellurium" title="Tellurium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Tellurium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Iodine" title="Iodine"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Iodine</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Xenon" title="Xenon"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Xenon</span></a> </td></tr> <tr style="border:none;padding:0;"> <td style="border:none;padding:0;"><a href="/wiki/Caesium" title="Caesium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Caesium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Barium" title="Barium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Barium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Lanthanum" title="Lanthanum"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Lanthanum</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Cerium" title="Cerium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Cerium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Praseodymium" title="Praseodymium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Praseodymium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Neodymium" title="Neodymium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Neodymium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Promethium" title="Promethium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Promethium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Samarium" title="Samarium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Samarium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Europium" title="Europium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Europium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Gadolinium" title="Gadolinium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Gadolinium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Terbium" title="Terbium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Terbium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Dysprosium" title="Dysprosium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Dysprosium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Holmium" title="Holmium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Holmium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Erbium" title="Erbium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Erbium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Thulium" title="Thulium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Thulium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Ytterbium" title="Ytterbium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Ytterbium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Lutetium" title="Lutetium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Lutetium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Hafnium" title="Hafnium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Hafnium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Tantalum" title="Tantalum"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Tantalum</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Tungsten" title="Tungsten"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Tungsten</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Rhenium" title="Rhenium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Rhenium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Osmium" title="Osmium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Osmium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Iridium" title="Iridium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Iridium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Platinum" title="Platinum"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Platinum</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Gold" title="Gold"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Gold</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Mercury_(element)" title="Mercury (element)"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Mercury (element)</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Thallium" title="Thallium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Thallium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Lead" title="Lead"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Lead</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Bismuth" title="Bismuth"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Bismuth</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Polonium" title="Polonium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Polonium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Astatine" title="Astatine"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Astatine</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Radon" title="Radon"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Radon</span></a> </td></tr> <tr> <td style="border:none;padding:0;"><a href="/wiki/Francium" title="Francium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Francium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Radium" title="Radium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#ff9999;">Radium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Actinium" title="Actinium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Actinium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Thorium" title="Thorium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Thorium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Protactinium" title="Protactinium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Protactinium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Uranium" title="Uranium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Uranium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Neptunium" title="Neptunium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Neptunium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Plutonium" title="Plutonium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Plutonium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Americium" title="Americium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Americium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Curium" title="Curium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Curium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Berkelium" title="Berkelium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Berkelium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Californium" title="Californium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Californium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Einsteinium" title="Einsteinium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Einsteinium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Fermium" title="Fermium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Fermium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Mendelevium" title="Mendelevium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Mendelevium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Nobelium" title="Nobelium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#9bff99;">Nobelium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Lawrencium" title="Lawrencium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Lawrencium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Rutherfordium" title="Rutherfordium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Rutherfordium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Dubnium" title="Dubnium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Dubnium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Seaborgium" title="Seaborgium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Seaborgium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Bohrium" title="Bohrium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Bohrium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Hassium" title="Hassium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Hassium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Meitnerium" title="Meitnerium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Meitnerium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Darmstadtium" title="Darmstadtium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Darmstadtium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Roentgenium" title="Roentgenium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Roentgenium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Copernicium" title="Copernicium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#99ccff;">Copernicium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Nihonium" title="Nihonium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Nihonium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Flerovium" title="Flerovium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Flerovium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Moscovium" title="Moscovium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Moscovium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Livermorium" title="Livermorium"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Livermorium</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Tennessine" title="Tennessine"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Tennessine</span></a> </td> <td style="border:none;padding:0;"><a href="/wiki/Oganesson" title="Oganesson"><span style="display:block;width:6px;height:8px;overflow:hidden;padding:0;color:transparent;background-color:#fdff8c;">Oganesson</span></a> </td></tr></tbody></table> </div></div> </div> <style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output 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.sidebar-list-title{padding:0 0.4em;text-align:left;font-weight:bold;line-height:1.6em;font-size:105%}.mw-parser-output .sidebar-list-title-c{padding:0 0.4em;text-align:center;margin:0 3.3em}@media(max-width:640px){body.mediawiki .mw-parser-output .sidebar{width:100%!important;clear:both;float:none!important;margin-left:0!important;margin-right:0!important}}body.skin--responsive .mw-parser-output .sidebar a>img{max-width:none!important}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}}</style><table class="sidebar sidebar-collapse nomobile nowraplinks hlist"><tbody><tr><td class="sidebar-pretitle">Part of <a href="/wiki/Category:Periodic_table" title="Category:Periodic table">a series</a> on the</td></tr><tr><th class="sidebar-title-with-pretitle"><a href="/wiki/Periodic_table" title="Periodic table">Periodic table</a></th></tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="border-top:1px solid #aaa;;color: var(--color-base)">Periodic table forms</div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><a href="/wiki/Periodic_table#Detailed_table" title="Periodic table">18-column</a></li> <li><a href="/wiki/Periodic_table#The_long-_or_32-column_table" title="Periodic table">32-column</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Types_of_periodic_tables" title="Types of periodic tables">Alternative</a><span class="nowrap"> </span>and<span class="nowrap"> </span><a href="/wiki/Extended_periodic_table" title="Extended periodic table">extended</a><span class="nowrap"> </span>forms</li></ul></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="border-top:1px solid #aaa;;color: var(--color-base)"><a href="/wiki/History_of_the_periodic_table" title="History of the periodic table">Periodic table history</a></div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><a href="/wiki/Dmitri_Mendeleev" title="Dmitri Mendeleev">D. Mendeleev</a> <ul><li><a href="/wiki/Dmitri_Mendeleev#Periodic_table" title="Dmitri Mendeleev">1871 table</a></li> <li><a href="/wiki/Mendeleev%27s_predicted_elements" title="Mendeleev's predicted elements">1869 predictions</a></li></ul></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Discovery_of_chemical_elements" title="Discovery of chemical elements">Discovery of elements</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><b><a href="/wiki/Naming_of_chemical_elements" title="Naming of chemical elements">Naming</a> and <a href="/wiki/List_of_chemical_element_name_etymologies" title="List of chemical element name etymologies">etymology</a></b></li></ul> <div style="clear:both;" class=""></div> <ul><li><ul><li><a href="/wiki/List_of_chemical_elements_named_after_people" title="List of chemical elements named after people">for people</a></li> <li><a href="/wiki/List_of_chemical_elements_named_after_places" title="List of chemical elements named after places">for places</a></li> <li><a href="/wiki/List_of_chemical_element_naming_controversies" title="List of chemical element naming controversies">controversies</a></li></ul></li></ul> <div style="clear:both;" class=""></div> <ul><li>(<a href="/wiki/Chemical_elements_in_East_Asian_languages" title="Chemical elements in East Asian languages">in East Asia</a>)</li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Systematic_element_name" title="Systematic element name">Systematic element names</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content" style="border-top:1px solid #aaa; text-align:left; background:#eeeeff;"> <div class="center" style="width:auto; margin-left:auto; margin-right:auto;"><b><a href="/wiki/Names_for_sets_of_chemical_elements" title="Names for sets of chemical elements">Sets of elements</a></b></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible"><div class="sidebar-list-title" style="border-top:1px solid #aaa;;color: var(--color-base)">By periodic table structure</div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><b><a href="/wiki/Group_(periodic_table)" title="Group (periodic table)">Groups</a> (1–18)</b></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Group_1_element" class="mw-redirect" title="Group 1 element"><span title="Group 1 — hydrogen group, all s¹ elements">1</span></a> (<a href="/wiki/Alkali_metal" title="Alkali metal"><span title="Part of group 1: Li, Na, K, Rb, Cs, Fr — lithium family, s¹ metals" class="nowrap"><i>alkali metals</i></span></a>)</li> <li><a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal"><span title="Group 2: Be, Mg, Ca, Sr, Ba, Ra — beryllium group, s² metals" class="nowrap">2 <i>(alkaline earth metals)</i></span></a></li> <li><a href="/wiki/Group_3_element" title="Group 3 element"><span title="Group 3: Sc, Y… — scandium group, s² d¹ metals">3</span></a></li> <li><a href="/wiki/Group_4_element" title="Group 4 element"><span title="Group 4: Ti, Zr, Hf, Rf — titanium and analogs, transition metals with 4 valence electrons">4</span></a></li> <li><a href="/wiki/Group_5_element" title="Group 5 element"><span title="Group 5: V, Nb, Ta, Db — vanadium and analogs, transition metals with 5 valence electrons">5</span></a></li> <li><a href="/wiki/Group_6_element" title="Group 6 element"><span title="Group 6: Cr, Mo, W, Sg — chromium and analogs, transition metals with 6 valence electrons">6</span></a></li> <li><a href="/wiki/Group_7_element" title="Group 7 element"><span title="Group 7: Mn, Tc, Re, Bh — manganese and analogs, transition metals with 7 valence electrons">7</span></a></li> <li><a href="/wiki/Group_8_element" title="Group 8 element"><span title="Group 8: Fe, Ru, Os, Hs — iron and analogs, transition metals with 8 valence electrons">8</span></a></li> <li><a href="/wiki/Group_9_element" title="Group 9 element"><span title="Group 9: Co, Rh, Ir, Mt — cobalt and analogs, transition metals with 9 valence electrons">9</span></a></li> <li><a href="/wiki/Group_10_element" title="Group 10 element"><span title="Group 10: Ni, Pd, Pt, Ds — nickel and analogs, transition metals with 10 valence electrons">10</span></a></li> <li><a href="/wiki/Group_11_element" title="Group 11 element"><span title="Group 11: Cu, Ag, Au, Rg — coinage metals, transition metals with 11 valence electrons">11</span></a></li> <li><a href="/wiki/Group_12_element" title="Group 12 element"><span title="Group 12: Zn, Cd, Hg, Cn — zinc group, s² d¹⁰ metals">12</span></a></li> <li><a href="/wiki/Boron_group" title="Boron group"><span title="Group 13: B, Al, Ga, In, Tl, Nh — boron group, s² p¹ elements">13</span></a></li> <li><a href="/wiki/Carbon_group" title="Carbon group"><span title="Group 14: C, Si, Ge, Sn, Pb, Fl — carbon group, s² p² elements">14</span></a></li> <li><a href="/wiki/Pnictogen" title="Pnictogen"><span title="Group 15: N, P, As, Sb, Bi, Mc — nitrogen group, s² p³ elements" class="nowrap">15 <i>(pnictogens)</i></span></a></li> <li><a href="/wiki/Chalcogen" title="Chalcogen"><span title="Group 16: O, S, Se, Te, Po, Lv — oxygen group, s² p⁴ elements" class="nowrap">16 <i>(chalcogens)</i></span></a></li> <li><a href="/wiki/Halogen" title="Halogen"><span title="Group 17: F, Cl, Br, I, At, Ts — fluorine group, s² p⁵ elements" class="nowrap">17 <i>(halogens)</i></span></a></li> <li><a href="/wiki/Noble_gas" title="Noble gas"><span title="Group 18: He, Ne, Ar, Kr, Xe, Rn, Og — elements having a complete valence shell" class="nowrap">18 <i>(noble gases)</i></span></a></li></ul> <div style="clear:both;" class=""></div> <ul><li><b><a href="/wiki/Period_(periodic_table)" title="Period (periodic table)">Periods</a> (1–7, ...)</b></li></ul> <div style="clear:both;" class=""></div> <ul><li><a class="mw-selflink selflink"><span title="Period 1: H, He, Z = 1–2">1</span></a></li> <li><a href="/wiki/Period_2_element" title="Period 2 element"><span title="Period 2: Li … Ne, Z = 3–10">2</span></a></li> <li><a href="/wiki/Period_3_element" title="Period 3 element"><span title="Period 3: Na … Ar, Z = 11–18">3</span></a></li> <li><a href="/wiki/Period_4_element" title="Period 4 element"><span title="Period 4: K … Kr, Z = 19–36">4</span></a></li> <li><a href="/wiki/Period_5_element" title="Period 5 element"><span title="Period 5: Rb … Xe, Z = 37–54">5</span></a></li> <li><a href="/wiki/Period_6_element" title="Period 6 element"><span title="Period 6: Cs … Rn, Z = 55–86">6</span></a></li> <li><a href="/wiki/Period_7_element" title="Period 7 element"><span title="Period 7: Fr … Og, Z = 87–118">7</span></a></li> <li><a href="/wiki/Extended_periodic_table" title="Extended periodic table"><span title="Periods 8+: Z = 119 …: Afbau, Fricke, and Pyykkö models">8+</span></a></li></ul> <div style="clear:both;" class=""></div> <ul><li><b><a href="/wiki/Block_(periodic_table)" title="Block (periodic table)">Blocks</a> (s, p, d, f, ...)</b></li></ul> <div style="clear:both;" class=""></div> <ul><li><ul><li><a href="/wiki/Atomic_orbital" title="Atomic orbital">Atomic orbitals</a></li> <li><a href="/wiki/Aufbau_principle" title="Aufbau principle">Aufbau principle</a></li></ul></li></ul></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="border-top:1px solid #aaa;;color: var(--color-base)">By <a href="/wiki/Properties_of_metals,_metalloids_and_nonmetals" title="Properties of metals, metalloids and nonmetals">metallic classification</a></div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><b><a href="/wiki/Metal" title="Metal">Metals</a></b></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Alkali_metal" title="Alkali metal">alkali</a></li> <li><a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal">alkaline earth</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Transition_metal" title="Transition metal">transition</a></li> <li><a href="/wiki/Post-transition_metal" title="Post-transition metal">post-transition</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Lanthanide" title="Lanthanide">lanthanide</a></li> <li><a href="/wiki/Actinide" title="Actinide">actinide</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><b><a href="/wiki/Metalloid" title="Metalloid">Metalloids</a></b></li></ul> <div style="clear:both;" class=""></div> <ul><li><ul><li><a href="/wiki/Dividing_line_between_metals_and_nonmetals" title="Dividing line between metals and nonmetals">dividing metals and nonmetals</a></li></ul></li></ul> <div style="clear:both;" class=""></div> <ul><li><b><a href="/wiki/Nonmetal" title="Nonmetal">Nonmetals</a></b></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Halogen" title="Halogen">nonmetal halogen</a></li> <li><a href="/wiki/Noble_gas" title="Noble gas">noble gas</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="border-top:1px solid #aaa;;color: var(--color-base)">By other characteristics</div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><a href="/wiki/Coinage_metals" title="Coinage metals">Coinage metals</a></li> <li><a href="/wiki/Platinum_group" title="Platinum group">Platinum-group metals</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Precious_metal" title="Precious metal">Precious metals</a></li> <li><a href="/wiki/Refractory_metals" title="Refractory metals">Refractory metals</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Heavy_metal_element" title="Heavy metal element">Heavy metals</a></li> <li><a href="/wiki/Light_metal" title="Light metal">Light metals</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Native_metal" title="Native metal">Native metals</a></li> <li><a href="/wiki/Noble_metal" title="Noble metal">Noble metals</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Main-group_element" title="Main-group element">Main-group elements</a></li> <li><a href="/wiki/Rare-earth_element" title="Rare-earth element">Rare-earth elements</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Transuranium_element" title="Transuranium element">Transuranium</a> elements</li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Major_actinide" title="Major actinide">Major</a>, <a href="/wiki/Minor_actinide" title="Minor actinide">minor</a> and <a href="/wiki/Superheavy_element" title="Superheavy element">trans-</a> actinides</li></ul></div></div></td> </tr><tr><td class="sidebar-content" style="border-top:1px solid #aaa; text-align:left; background:#eeeeff;"> <div class="center" style="width:auto; margin-left:auto; margin-right:auto;"><b><a href="/wiki/Chemical_element" title="Chemical element">Elements</a></b></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="border-top:1px solid #aaa;;color: var(--color-base)"><a href="/wiki/List_of_chemical_elements" title="List of chemical elements">List of chemical elements</a></div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><a href="/wiki/Abundance_of_the_chemical_elements" title="Abundance of the chemical elements">by abundance</a> (<a href="/wiki/Composition_of_the_human_body" title="Composition of the human body">in human body</a>)</li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/List_of_elements_by_atomic_properties" title="List of elements by atomic properties">by atomic properties</a></li> <li><a href="/wiki/List_of_elements_by_stability_of_isotopes" title="List of elements by stability of isotopes">by isotope stability</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Chemical_symbol" title="Chemical symbol">by symbol</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="border-top:1px solid #aaa;;color: var(--color-base)"><a href="/wiki/Chemical_element#Properties" title="Chemical element">Properties of elements</a></div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><a href="/wiki/Relative_atomic_mass" title="Relative atomic mass">Relative atomic mass</a></li> <li><a href="/wiki/Periodic_table_(crystal_structure)" title="Periodic table (crystal structure)">Crystal structure</a></li></ul> <div style="clear:both;" class=""></div> <ul><li>Electron <a href="/wiki/Electron_affinity" title="Electron affinity">affinity</a></li> <li><a href="/wiki/Electron_configuration" title="Electron configuration">configuration</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Electronegativity" title="Electronegativity">Electronegativity</a> (<a href="/wiki/Electronegativity#Allen_electronegativity" title="Electronegativity">Allen</a>, <a href="/wiki/Electronegativity#Pauling_electronegativity" title="Electronegativity">Pauling</a>)</li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Goldschmidt_classification" title="Goldschmidt classification">Goldschmidt classification</a></li></ul> <div style="clear:both;" class=""></div> <ul><li><a href="/wiki/Mineral_(nutrient)" title="Mineral (nutrient)">Nutrition</a></li> <li><a href="/wiki/Valence_(chemistry)" title="Valence (chemistry)">Valence</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="border-top:1px solid #aaa;;color: var(--color-base)">Data pages for elements</div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><a href="/wiki/Abundances_of_the_elements_(data_page)" title="Abundances of the elements (data page)">Abundance</a></li> <li><a href="/wiki/Atomic_radii_of_the_elements_(data_page)" title="Atomic radii of the elements (data page)">Atomic radius</a></li> <li><a href="/wiki/Boiling_points_of_the_elements_(data_page)" title="Boiling points of the elements (data page)">Boiling point</a></li> <li><a href="/wiki/Critical_points_of_the_elements_(data_page)" title="Critical points of the elements (data page)">Critical point</a></li> <li><a href="/wiki/Densities_of_the_elements_(data_page)" title="Densities of the elements (data page)">Density</a></li> <li><a href="/wiki/Elastic_properties_of_the_elements_(data_page)" title="Elastic properties of the elements (data page)">Elasticity</a></li> <li><a href="/wiki/Electrical_resistivities_of_the_elements_(data_page)" title="Electrical resistivities of the elements (data page)">Electrical resistivity</a></li> <li>Electron <a href="/wiki/Electron_affinity_(data_page)" title="Electron affinity (data page)">affinity</a> / <a href="/wiki/Electron_configurations_of_the_elements_(data_page)" title="Electron configurations of the elements (data page)">configuration</a></li> <li><a href="/wiki/Electronegativities_of_the_elements_(data_page)" title="Electronegativities of the elements (data page)">Electronegativity</a></li> <li><a href="/wiki/Hardnesses_of_the_elements_(data_page)" title="Hardnesses of the elements (data page)">Hardness</a></li> <li>Heat <a href="/wiki/Heat_capacities_of_the_elements_(data_page)" title="Heat capacities of the elements (data page)">capacity</a> / <a href="/wiki/Heats_of_fusion_of_the_elements_(data_page)" title="Heats of fusion of the elements (data page)">of fusion</a> / <a href="/wiki/Heats_of_vaporization_of_the_elements_(data_page)" title="Heats of vaporization of the elements (data page)">of vaporization</a></li> <li><a href="/wiki/Ionization_energies_of_the_elements_(data_page)" title="Ionization energies of the elements (data page)">Ionization energy</a></li> <li><a href="/wiki/Melting_points_of_the_elements_(data_page)" title="Melting points of the elements (data page)">Melting point</a></li> <li><a href="/wiki/Oxidation_state" title="Oxidation state">Oxidation state</a></li> <li><a href="/wiki/Speeds_of_sound_of_the_elements" title="Speeds of sound of the elements">Speed of sound</a></li> <li>Thermal <a href="/wiki/Thermal_conductivities_of_the_elements_(data_page)" title="Thermal conductivities of the elements (data page)">conductivity</a> / <a href="/wiki/Thermal_expansivities_of_the_elements" title="Thermal expansivities of the elements">expansion coefficient</a></li> <li><a href="/wiki/Vapor_pressures_of_the_elements_(data_page)" title="Vapor pressures of the elements (data page)">Vapor pressure</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content" style="border-top:1px solid #aaa; border-bottom:1px solid #aaa; background:#eeeeff;"> <ul><li><b><a href="/wiki/Category:Periodic_table" title="Category:Periodic table">Category</a></b></li> <li><b><a href="/wiki/Portal:Chemistry" title="Portal:Chemistry">Chemistry Portal</a></b></li></ul></td> </tr><tr><td class="sidebar-navbar"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Sidebar_periodic_table" title="Template:Sidebar periodic table"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Sidebar_periodic_table" title="Template talk:Sidebar periodic table"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Sidebar_periodic_table" title="Special:EditPage/Template:Sidebar periodic table"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <p>A <b>period 1 element</b> is one of the <a href="/wiki/Chemical_element" title="Chemical element">chemical elements</a> in the first row (or <a href="/wiki/Periodic_table_period" class="mw-redirect" title="Periodic table period">period</a>) of the <a href="/wiki/Periodic_table" title="Periodic table">periodic table of the chemical elements</a>. The periodic table is laid out in rows to illustrate periodic (recurring) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that analog elements fall into the same vertical columns. The first period contains fewer elements than any other row in the table, with only two: <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a> and <a href="/wiki/Helium" title="Helium">helium</a>. This situation can be explained by modern theories of <a href="/wiki/Atomic_structure" class="mw-redirect" title="Atomic structure">atomic structure</a>. In a <a href="/wiki/Quantum_mechanics" title="Quantum mechanics">quantum mechanical</a> description of atomic structure, this period corresponds to the filling of the <a href="/wiki/Atomic_orbital" title="Atomic orbital">1s orbital</a>. Period 1 elements obey the <a href="/wiki/Octet_rule#Exceptions" title="Octet rule">duet rule</a> in that they need two <a href="/wiki/Electron" title="Electron">electrons</a> to complete their <a href="/wiki/Valence_shell" class="mw-redirect" title="Valence shell">valence shell</a>. </p><p>Hydrogen and helium are <a href="/wiki/Big_Bang_nucleosynthesis" title="Big Bang nucleosynthesis">the oldest</a> and the most abundant elements in the <a href="/wiki/Universe" title="Universe">universe</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Periodic_trends">Periodic trends</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_1_element&action=edit&section=1" title="Edit section: Periodic trends"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>All other periods in the periodic table contain at least eight elements, and it is often helpful to consider <a href="/wiki/Periodic_trends" title="Periodic trends">periodic trends</a> across the period. However, period 1 contains only two elements, so this concept does not apply here.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (August 2019)">citation needed</span></a></i>]</sup> </p><p>In terms of vertical trends down groups, helium can be seen as a typical <a href="/wiki/Noble_gas" title="Noble gas">noble gas</a> at the head of the IUPAC <a href="/wiki/Group_18" class="mw-redirect" title="Group 18">group 18</a>, but as discussed below, hydrogen's chemistry is unique and it is not easily assigned to any group.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Position_of_period_1_elements_in_the_periodic_table">Position of period 1 elements in the periodic table</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_1_element&action=edit&section=2" title="Edit section: Position of period 1 elements in the periodic table"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The first <a href="/wiki/Electron_shell" title="Electron shell">electron shell</a>, <span class="texhtml"><a href="/wiki/Principal_quantum_number" title="Principal quantum number"><i>n</i></a> = 1</span>, consists of only one orbital, and the maximum number of <a href="/wiki/Valence_electron" title="Valence electron">valence electrons</a> that a period 1 element can accommodate is two, both in the 1s orbital. The valence shell lacks "p" or any other kind of orbitals due to the <a href="/wiki/Hydrogen-like_atom#Quantum_numbers" title="Hydrogen-like atom">general <span class="texhtml"><i>l</i> < <i>n</i></span> constraint</a> on the <a href="/wiki/Quantum_number" title="Quantum number">quantum numbers</a>. Therefore, period 1 has exactly two elements. Although both hydrogen and helium are in the <a href="/wiki/S-block" class="mw-redirect" title="S-block">s-block</a>, neither of them behaves similarly to other s-block elements. Their behaviour is so different from the other s-block elements that there is considerable disagreement over where these two elements should be placed in the periodic table. </p><p>Simply following electron configurations, hydrogen (electronic configuration 1s<sup>1</sup>) and helium (1s<sup>2</sup>) should be placed in groups 1 and 2, above lithium (1s<sup>2</sup>2s<sup>1</sup>) and beryllium (1s<sup>2</sup>2s<sup>2</sup>).<sup id="cite_ref-Gray12_2-0" class="reference"><a href="#cite_note-Gray12-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> While such a placement is common for hydrogen, it is rarely used for helium outside of the context of illustrating the electron configurations. Usually, hydrogen is placed in group 1, and helium in group 18: this is the placement found on the IUPAC periodic table.<sup id="cite_ref-IUPAC-redbook_3-0" class="reference"><a href="#cite_note-IUPAC-redbook-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Some variation can be found on both these matters.<sup id="cite_ref-KW_4-0" class="reference"><a href="#cite_note-KW-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>Like the group 1 metals, hydrogen has one electron in its outermost shell<sup id="cite_ref-Gray12_2-1" class="reference"><a href="#cite_note-Gray12-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> and typically loses its only electron in chemical reactions.<sup id="cite_ref-Vlasov_5-0" class="reference"><a href="#cite_note-Vlasov-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> It has some metal-like chemical properties, being able to displace some metals from their <a href="/wiki/Salt_(chemistry)" title="Salt (chemistry)">salts</a>.<sup id="cite_ref-Vlasov_5-1" class="reference"><a href="#cite_note-Vlasov-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> But hydrogen forms a diatomic nonmetallic gas at standard conditions, unlike the alkali metals which are reactive solid metals. This and hydrogen's formation of <a href="/wiki/Hydride" title="Hydride">hydrides</a>, in which it gains an electron, brings it close to the properties of the <a href="/wiki/Halogen" title="Halogen">halogens</a> which do the same<sup id="cite_ref-Vlasov_5-2" class="reference"><a href="#cite_note-Vlasov-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> (though it is rarer for hydrogen to form H<sup>−</sup> than H<sup>+</sup>).<sup id="cite_ref-raynercanham_6-0" class="reference"><a href="#cite_note-raynercanham-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Moreover, the lightest two halogens (<a href="/wiki/Fluorine" title="Fluorine">fluorine</a> and <a href="/wiki/Chlorine" title="Chlorine">chlorine</a>) are gaseous like hydrogen at standard conditions.<sup id="cite_ref-Vlasov_5-3" class="reference"><a href="#cite_note-Vlasov-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> Some properties of hydrogen are not a good fit for either group: hydrogen is neither highly oxidising nor highly reducing and is not reactive with water.<sup id="cite_ref-raynercanham_6-1" class="reference"><a href="#cite_note-raynercanham-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Hydrogen thus has properties corresponding to both those of the alkali metals and the halogens, but matches neither group perfectly, and is thus difficult to place by its chemistry.<sup id="cite_ref-Vlasov_5-4" class="reference"><a href="#cite_note-Vlasov-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> Therefore, while the electronic placement of hydrogen in group 1 predominates, some rarer arrangements show either hydrogen in group 17,<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> duplicate hydrogen in both groups 1 and 17,<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Kaesz_9-0" class="reference"><a href="#cite_note-Kaesz-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> or float it separately from all groups.<sup id="cite_ref-Kaesz_9-1" class="reference"><a href="#cite_note-Kaesz-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-GE_10-0" class="reference"><a href="#cite_note-GE-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-KW_4-1" class="reference"><a href="#cite_note-KW-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The possibility of "floating" hydrogen has nonetheless been criticised by <a href="/wiki/Eric_Scerri" title="Eric Scerri">Eric Scerri</a>, who points out that removing it from all groups suggests that it is being excluded from the periodic law, when all elements should be subject to that law.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> A few authors have advocated more unusual placements for hydrogen, such as group 13 or group 14, on the grounds of trends in ionisation energy, electron affinity, and electronegativity.<sup id="cite_ref-raynercanham_6-2" class="reference"><a href="#cite_note-raynercanham-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>Helium is an unreactive noble gas at standard conditions, and has a full outer shell: these properties are like the noble gases in group 18, but not at all like the reactive alkaline earth metals of group 2. Therefore, helium is nearly universally placed in group 18<sup id="cite_ref-IUPAC-redbook_3-1" class="reference"><a href="#cite_note-IUPAC-redbook-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> which its properties best match.<sup id="cite_ref-KW_4-2" class="reference"><a href="#cite_note-KW-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> However, helium only has two outer electrons in its outer shell, whereas the other noble gases have eight; and it is an s-block element, whereas all other noble gases are p-block elements. Also, solid helium crystallises in a <a href="/wiki/Hexagonal_close-packed" class="mw-redirect" title="Hexagonal close-packed">hexagonal close-packed</a> structure, which matches beryllium and magnesium in group 2, but not the other noble gases in group 18.<sup id="cite_ref-Kurushkin_12-0" class="reference"><a href="#cite_note-Kurushkin-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> In these ways helium better matches the alkaline earth metals.<sup id="cite_ref-Gray12_2-2" class="reference"><a href="#cite_note-Gray12-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-KW_4-3" class="reference"><a href="#cite_note-KW-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Therefore, tables with both hydrogen and helium floating outside all groups may rarely be encountered.<sup id="cite_ref-GE_10-1" class="reference"><a href="#cite_note-GE-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-KW_4-4" class="reference"><a href="#cite_note-KW-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>A few chemists, such as <a href="/wiki/Henry_Bent" class="mw-redirect" title="Henry Bent">Henry Bent</a>, have advocated that the electronic placement in group 2 be adopted for helium.<sup id="cite_ref-PTSS_13-0" class="reference"><a href="#cite_note-PTSS-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Kurushkin_12-1" class="reference"><a href="#cite_note-Kurushkin-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> This assignment is also found in <a href="/wiki/Charles_Janet" title="Charles Janet">Charles Janet</a>'s left-step table. Arguments for this often rest on the first-row anomaly trend (s >> p > d > f), which states that the first element of each group often behaves quite differently from the succeeding ones: the difference is largest in the s-block (H and He), is moderate for the p-block (B to Ne), and is less pronounced for the d- and f-blocks.<sup id="cite_ref-PTSS_13-1" class="reference"><a href="#cite_note-PTSS-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> Thus helium as the first s<sup>2</sup> element before the alkaline earth metals stands out as anomalous in a way that helium as the first noble gas does not.<sup id="cite_ref-PTSS_13-2" class="reference"><a href="#cite_note-PTSS-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> The normalized ionization potentials and electron affinities show better trends with helium in group 2 than in group 18; helium is expected to be slightly more reactive than neon (which breaks the general trend of reactivity in the noble gases, where the heavier ones are more reactive); and predicted helium compounds often lack neon analogues even theoretically, but sometimes have beryllium analogues.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading2"><h2 id="Elements">Elements</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_1_element&action=edit&section=3" title="Edit section: Elements"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <table class="wikitable"> <tbody><tr> <th colspan="3"><a href="/wiki/Chemical_element" title="Chemical element">Chemical element</a></th> <th><a href="/wiki/Block_(periodic_table)" title="Block (periodic table)">Block</a></th> <th><a href="/wiki/Electron_configuration" title="Electron configuration">Electron configuration</a> </th></tr> <tr style="background-color: #ff9999"> <td>1</td> <td><b>H</b></td> <td><a href="/wiki/Hydrogen" title="Hydrogen">Hydrogen</a></td> <td><a href="/wiki/S-block" class="mw-redirect" title="S-block">s-block</a></td> <td>1s<sup>1</sup> </td></tr> <tr style="background-color: #ff9999"> <td>2</td> <td><b>He</b></td> <td><a href="/wiki/Helium" title="Helium">Helium</a></td> <td><a href="/wiki/S-block" class="mw-redirect" title="S-block">s-block</a></td> <td>1s<sup>2</sup> </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="Hydrogen">Hydrogen</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_1_element&action=edit&section=4" title="Edit section: Hydrogen"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Hydrogen" title="Hydrogen">Hydrogen</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Hydrogen_discharge_tube.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Hydrogen_discharge_tube.jpg/150px-Hydrogen_discharge_tube.jpg" decoding="async" width="150" height="50" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Hydrogen_discharge_tube.jpg/225px-Hydrogen_discharge_tube.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Hydrogen_discharge_tube.jpg/300px-Hydrogen_discharge_tube.jpg 2x" data-file-width="3000" data-file-height="1000" /></a><figcaption>Hydrogen discharge tube</figcaption></figure> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Deuterium_discharge_tube.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Deuterium_discharge_tube.jpg/150px-Deuterium_discharge_tube.jpg" decoding="async" width="150" height="50" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Deuterium_discharge_tube.jpg/225px-Deuterium_discharge_tube.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Deuterium_discharge_tube.jpg/300px-Deuterium_discharge_tube.jpg 2x" data-file-width="3000" data-file-height="1000" /></a><figcaption>Deuterium discharge tube</figcaption></figure> <p>Hydrogen (H) is the <a href="/wiki/Chemical_element" title="Chemical element">chemical element</a> with <a href="/wiki/Atomic_number" title="Atomic number">atomic number</a> 1. At <a href="/wiki/Standard_temperature_and_pressure" title="Standard temperature and pressure">standard temperature and pressure</a>, hydrogen is a colorless, odorless, <a href="/wiki/Nonmetal_(chemistry)" class="mw-redirect" title="Nonmetal (chemistry)">nonmetallic</a>, tasteless, highly <a href="/wiki/Combustion" title="Combustion">flammable</a> <a href="/wiki/Diatomic_molecule" title="Diatomic molecule">diatomic</a> <a href="/wiki/Gas" title="Gas">gas</a> with the <a href="/wiki/Molecular_formula" class="mw-redirect" title="Molecular formula">molecular formula</a> H<sub>2</sub>. With an <a href="/wiki/Atomic_mass" title="Atomic mass">atomic mass</a> of 1.00794 amu, hydrogen is the lightest element.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p><p>Hydrogen is the most <a href="/wiki/Abundance_of_the_chemical_elements" title="Abundance of the chemical elements">abundant</a> of the chemical elements, constituting roughly 75% of the universe's elemental mass.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Star" title="Star">Stars</a> in the <a href="/wiki/Main_sequence" title="Main sequence">main sequence</a> are mainly composed of hydrogen in its <a href="/wiki/Plasma_(physics)" title="Plasma (physics)">plasma</a> state. Elemental hydrogen is relatively rare on <a href="/wiki/Earth" title="Earth">Earth</a>, and is industrially produced from <a href="/wiki/Hydrocarbon" title="Hydrocarbon">hydrocarbons</a> such as methane, after which most elemental hydrogen is used "captively" (meaning locally at the production site), with the largest markets almost equally divided between <a href="/wiki/Fossil_fuel" title="Fossil fuel">fossil fuel</a> upgrading, such as <a href="/wiki/Hydrocracking" class="mw-redirect" title="Hydrocracking">hydrocracking</a>, and <a href="/wiki/Ammonia" title="Ammonia">ammonia</a> production, mostly for the fertilizer market. Hydrogen may be produced from water using the process of <a href="/wiki/Electrolysis" title="Electrolysis">electrolysis</a>, but this process is significantly more expensive commercially than <a href="/wiki/Hydrogen_production" title="Hydrogen production">hydrogen production</a> from natural gas.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> </p><p>The most common naturally occurring <a href="/wiki/Isotope" title="Isotope">isotope</a> of hydrogen, known as <a href="/wiki/Hydrogen-1" class="mw-redirect" title="Hydrogen-1">protium</a>, has a single <a href="/wiki/Proton" title="Proton">proton</a> and no <a href="/wiki/Neutron" title="Neutron">neutrons</a>.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> In <a href="/wiki/Ionic_compound" class="mw-redirect" title="Ionic compound">ionic compounds</a>, it can take on either a positive charge, becoming a <a href="/wiki/Ion" title="Ion">cation</a> composed of a bare proton, or a negative charge, becoming an <a href="/wiki/Ion" title="Ion">anion</a> known as a <a href="/wiki/Hydride" title="Hydride">hydride</a>. Hydrogen can form compounds with most elements and is present in <a href="/wiki/Water" title="Water">water</a> and most <a href="/wiki/Organic_compound" title="Organic compound">organic compounds</a>.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> It plays a particularly important role in <a href="/wiki/Acid-base_reaction_theories" class="mw-redirect" title="Acid-base reaction theories">acid-base chemistry</a>, in which many reactions involve the exchange of protons between soluble molecules.<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> As the only neutral atom for which the <a href="/wiki/Schr%C3%B6dinger_equation" title="Schrödinger equation">Schrödinger equation</a> can be solved analytically, study of the energetics and <a href="/wiki/Atomic_spectrum" class="mw-redirect" title="Atomic spectrum">spectrum</a> of the hydrogen atom has played a key role in the development of <a href="/wiki/Quantum_mechanics" title="Quantum mechanics">quantum mechanics</a>.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> </p><p>The interactions of hydrogen with various metals are very important in <a href="/wiki/Metallurgy" title="Metallurgy">metallurgy</a>, as many metals can suffer <a href="/wiki/Hydrogen_embrittlement" title="Hydrogen embrittlement">hydrogen embrittlement</a>,<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> and in developing safe ways to store it for use as a fuel.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> Hydrogen is highly soluble in many compounds composed of <a href="/wiki/Rare_earth_element" class="mw-redirect" title="Rare earth element">rare earth metals</a> and <a href="/wiki/Transition_metal" title="Transition metal">transition metals</a><sup id="cite_ref-Takeshita_29-0" class="reference"><a href="#cite_note-Takeshita-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> and can be dissolved in both <a href="/wiki/Crystalline" class="mw-redirect" title="Crystalline">crystalline</a> and <a href="/wiki/Amorphous_solid" title="Amorphous solid">amorphous</a> metals.<sup id="cite_ref-Kirchheim1_30-0" class="reference"><a href="#cite_note-Kirchheim1-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> Hydrogen solubility in metals is influenced by local distortions or impurities in the metal <a href="/wiki/Crystal_lattice" class="mw-redirect" title="Crystal lattice">crystal lattice</a>.<sup id="cite_ref-Kirchheim2_31-0" class="reference"><a href="#cite_note-Kirchheim2-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Helium">Helium</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_1_element&action=edit&section=5" title="Edit section: Helium"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Helium" title="Helium">Helium</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Helium_discharge_tube.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/82/Helium_discharge_tube.jpg/150px-Helium_discharge_tube.jpg" decoding="async" width="150" height="100" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/82/Helium_discharge_tube.jpg/225px-Helium_discharge_tube.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/82/Helium_discharge_tube.jpg/300px-Helium_discharge_tube.jpg 2x" data-file-width="3008" data-file-height="2008" /></a><figcaption>Helium discharge tube</figcaption></figure> <p>Helium (He) is a colorless, odorless, tasteless, non-toxic, <a href="/wiki/Inert_gas" title="Inert gas">inert</a> <a href="/wiki/Monatomic" class="mw-redirect" title="Monatomic">monatomic</a> chemical element that heads the <a href="/wiki/Noble_gas" title="Noble gas">noble gas</a> series in the <a href="/wiki/Periodic_table" title="Periodic table">periodic table</a> and whose <a href="/wiki/Atomic_number" title="Atomic number">atomic number</a> is 2.<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> Its <a href="/wiki/Boiling_point" title="Boiling point">boiling</a> and <a href="/wiki/Melting_point" title="Melting point">melting</a> points are the lowest among the elements and it exists only as a <a href="/wiki/Gas" title="Gas">gas</a> except in extreme conditions.<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> </p><p>Helium was discovered in 1868 by French astronomer <a href="/wiki/Pierre_Janssen" title="Pierre Janssen">Pierre Janssen</a>, who <a href="/wiki/Discovery_of_the_chemical_elements" class="mw-redirect" title="Discovery of the chemical elements">first detected</a> the substance as an unknown yellow <a href="/wiki/Spectroscopy" title="Spectroscopy">spectral line</a> signature in light from a <a href="/wiki/Solar_eclipse" title="Solar eclipse">solar eclipse</a>.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> In 1903, large reserves of helium were found in the <a href="/wiki/Natural_gas_field" class="mw-redirect" title="Natural gas field">natural gas fields</a> of the United States, which is by far the largest supplier of the gas.<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> The substance is used in <a href="/wiki/Cryogenics" title="Cryogenics">cryogenics</a>,<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> in deep-sea breathing systems,<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> to cool <a href="/wiki/Superconducting_magnet" title="Superconducting magnet">superconducting magnets</a>, in <a href="/wiki/Helium_dating" title="Helium dating">helium dating</a>,<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> for inflating <a href="/wiki/Balloon" title="Balloon">balloons</a>,<sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> for providing lift in <a href="/wiki/Airship" title="Airship">airships</a>,<sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> and as a protective gas for industrial uses such as <a href="/wiki/Arc_welding" title="Arc welding">arc welding</a> and growing <a href="/wiki/Silicon" title="Silicon">silicon</a> wafers.<sup id="cite_ref-41" class="reference"><a href="#cite_note-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> Inhaling a small <a href="/wiki/Volume" title="Volume">volume</a> of the gas temporarily changes the timbre and quality of the human voice.<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> The behavior of liquid helium-4's two fluid phases, helium I and helium II, is important to researchers studying <a href="/wiki/Quantum_mechanics" title="Quantum mechanics">quantum mechanics</a> and the phenomenon of <a href="/wiki/Superfluidity" title="Superfluidity">superfluidity</a> in particular,<sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> and to those looking at the effects that temperatures near <a href="/wiki/Absolute_zero" title="Absolute zero">absolute zero</a> have on <a href="/wiki/Matter" title="Matter">matter</a>, such as with <a href="/wiki/Superconductivity" title="Superconductivity">superconductivity</a>.<sup id="cite_ref-44" class="reference"><a href="#cite_note-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> </p><p>Helium is the second lightest element and is the second most <a href="/wiki/Chemical_abundance" class="mw-redirect" title="Chemical abundance">abundant</a> in the observable universe.<sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> Most helium was formed during the <a href="/wiki/Big_Bang" title="Big Bang">Big Bang</a>, but new helium is being created as a result of the <a href="/wiki/Nuclear_fusion" title="Nuclear fusion">nuclear fusion</a> of hydrogen in <a href="/wiki/Star" title="Star">stars</a>.<sup id="cite_ref-46" class="reference"><a href="#cite_note-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> On <a href="/wiki/Earth" title="Earth">Earth</a>, helium is relatively rare and is created by the natural <a href="/wiki/Radioactive_decay" title="Radioactive decay">decay</a> of some radioactive elements<sup id="cite_ref-47" class="reference"><a href="#cite_note-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> because the <a href="/wiki/Alpha_particle" title="Alpha particle">alpha particles</a> that are emitted consist of helium <a href="/wiki/Atomic_nucleus" title="Atomic nucleus">nuclei</a>. This radiogenic helium is trapped with <a href="/wiki/Natural_gas" title="Natural gas">natural gas</a> in concentrations of up to seven percent by volume,<sup id="cite_ref-48" class="reference"><a href="#cite_note-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> from which it is extracted commercially by a low-temperature separation process called <a href="/wiki/Fractional_distillation" title="Fractional distillation">fractional distillation</a>.<sup id="cite_ref-49" class="reference"><a href="#cite_note-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_1_element&action=edit&section=6" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFMichael_Laing2006" class="citation journal cs1">Michael Laing (2006). "Where to Put Hydrogen in a Periodic Table?". <i>Foundations of Chemistry</i>. <b>9</b> (2): 127–137. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs10698-006-9027-5">10.1007/s10698-006-9027-5</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:93781427">93781427</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Foundations+of+Chemistry&rft.atitle=Where+to+Put+Hydrogen+in+a+Periodic+Table%3F&rft.volume=9&rft.issue=2&rft.pages=127-137&rft.date=2006&rft_id=info%3Adoi%2F10.1007%2Fs10698-006-9027-5&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A93781427%23id-name%3DS2CID&rft.au=Michael+Laing&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-Gray12-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-Gray12_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Gray12_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Gray12_2-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text">Gray, p. 12</span> </li> <li id="cite_note-IUPAC-redbook-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-IUPAC-redbook_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-IUPAC-redbook_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://iupac.org/what-we-do/periodic-table-of-elements/">"Periodic Table of Elements"</a>. <i>iupac.org</i>. 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Retrieved <span class="nowrap">3 April</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=iupac.org&rft.atitle=Periodic+Table+of+Elements&rft.date=2021&rft_id=https%3A%2F%2Fiupac.org%2Fwhat-we-do%2Fperiodic-table-of-elements%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-KW-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-KW_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-KW_4-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-KW_4-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-KW_4-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-KW_4-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWothersKeeler,_Wothers2008" class="citation book cs1">Wothers, Peter; Keeler, Wothers (2008). <i>Chemical structure and reactivity : an integrated approach</i>. Oxford: Oxford University Press. p. 259. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-19-928930-1" title="Special:BookSources/978-0-19-928930-1"><bdi>978-0-19-928930-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Chemical+structure+and+reactivity+%3A+an+integrated+approach&rft.place=Oxford&rft.pages=259&rft.pub=Oxford+University+Press&rft.date=2008&rft.isbn=978-0-19-928930-1&rft.aulast=Wothers&rft.aufirst=Peter&rft.au=Keeler%2C+Wothers&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-Vlasov-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-Vlasov_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Vlasov_5-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Vlasov_5-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Vlasov_5-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Vlasov_5-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFVlasovTrifonov1970" class="citation book cs1">Vlasov, L.; Trifonov, D. (1970). <i>107 Stories About Chemistry</i>. Translated by Sobolev, D. Mir Publishers. pp. 23–27. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-8285-5067-3" title="Special:BookSources/978-0-8285-5067-3"><bdi>978-0-8285-5067-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=107+Stories+About+Chemistry&rft.pages=23-27&rft.pub=Mir+Publishers&rft.date=1970&rft.isbn=978-0-8285-5067-3&rft.aulast=Vlasov&rft.aufirst=L.&rft.au=Trifonov%2C+D.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-raynercanham-6"><span class="mw-cite-backlink">^ <a href="#cite_ref-raynercanham_6-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-raynercanham_6-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-raynercanham_6-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRayner-Canham2020" class="citation book cs1">Rayner-Canham, Geoffrey (2020). <i>The Periodic Table: Past, Present, Future</i>. World Scientific. pp. 71–84. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9789811218507" title="Special:BookSources/9789811218507"><bdi>9789811218507</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Periodic+Table%3A+Past%2C+Present%2C+Future&rft.pages=71-84&rft.pub=World+Scientific&rft.date=2020&rft.isbn=9789811218507&rft.aulast=Rayner-Canham&rft.aufirst=Geoffrey&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFClaydenGreevesWarrenWothers2001" class="citation book cs1"><a href="/wiki/Jonathan_Clayden" title="Jonathan Clayden">Clayden, Jonathan</a>; Greeves, Nick; <a href="/wiki/Stuart_Warren" title="Stuart Warren">Warren, Stuart</a>; <a href="/wiki/Peter_Wothers" title="Peter Wothers">Wothers, Peter</a> (2001). <i>Organic Chemistry</i> (1st ed.). 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Retrieved <span class="nowrap">2008-07-15</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Popular+Science&rft.atitle=The+Return+of+the+Blimp&rft.date=2008-07-10&rft.au=Jiwatram%2C+Jaya&rft_id=http%3A%2F%2Fwww.popsci.com%2Fmilitary-aviation-space%2Farticle%2F2008-07%2Freturn-blimp&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-41"><span class="mw-cite-backlink"><b><a href="#cite_ref-41">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation journal cs1">"When good GTAW arcs drift; drafty conditions are bad for welders and their GTAW arcs". <i>Welding Design & Fabrication</i>. 2005-02-01.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Welding+Design+%26+Fabrication&rft.atitle=When+good+GTAW+arcs+drift%3B+drafty+conditions+are+bad+for+welders+and+their+GTAW+arcs.&rft.date=2005-02-01&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-42"><span class="mw-cite-backlink"><b><a href="#cite_ref-42">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMontgomery,_Craig2006" class="citation web cs1">Montgomery, Craig (2006-09-04). <a rel="nofollow" class="external text" href="http://www.sciam.com/article.cfm?id=why-does-inhaling-helium">"Why does inhaling helium make one's voice sound strange?"</a>. <i>Scientific American</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2008-07-15</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Scientific+American&rft.atitle=Why+does+inhaling+helium+make+one%27s+voice+sound+strange%3F&rft.date=2006-09-04&rft.au=Montgomery%2C+Craig&rft_id=http%3A%2F%2Fwww.sciam.com%2Farticle.cfm%3Fid%3Dwhy-does-inhaling-helium&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-43"><span class="mw-cite-backlink"><b><a href="#cite_ref-43">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.sciencedaily.com/releases/2004/09/040903085531.htm">"Probable Discovery Of A New, Supersolid, Phase Of Matter"</a>. Science Daily. 2004-09-03<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-07-15</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Probable+Discovery+Of+A+New%2C+Supersolid%2C+Phase+Of+Matter&rft.pub=Science+Daily&rft.date=2004-09-03&rft_id=https%3A%2F%2Fwww.sciencedaily.com%2Freleases%2F2004%2F09%2F040903085531.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-44"><span class="mw-cite-backlink"><b><a href="#cite_ref-44">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBrowne,_Malcolm_W.1979" class="citation news cs1">Browne, Malcolm W. (1979-08-21). "Scientists See Peril In Wasting Helium; Scientists See Peril in Waste of Helium". <i>The New York Times</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+New+York+Times&rft.atitle=Scientists+See+Peril+In+Wasting+Helium%3B+Scientists+See+Peril+in+Waste+of+Helium&rft.date=1979-08-21&rft.au=Browne%2C+Malcolm+W.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-45"><span class="mw-cite-backlink"><b><a href="#cite_ref-45">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.webelements.com/helium/geology.html">"Helium: geological information"</a>. WebElements<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-07-15</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Helium%3A+geological+information&rft.pub=WebElements&rft_id=http%3A%2F%2Fwww.webelements.com%2Fhelium%2Fgeology.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-46"><span class="mw-cite-backlink"><b><a href="#cite_ref-46">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCox,_Tony1990" class="citation web cs1">Cox, Tony (1990-02-03). <a rel="nofollow" class="external text" href="https://www.newscientist.com/article/mg12517027.000-origin-of-the-chemical-elements.html">"Origin of the chemical elements"</a>. <i>New Scientist</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2008-07-15</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=New+Scientist&rft.atitle=Origin+of+the+chemical+elements&rft.date=1990-02-03&rft.au=Cox%2C+Tony&rft_id=https%3A%2F%2Fwww.newscientist.com%2Farticle%2Fmg12517027.000-origin-of-the-chemical-elements.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-47"><span class="mw-cite-backlink"><b><a href="#cite_ref-47">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation news cs1">"Helium supply deflated: production shortages mean some industries and partygoers must squeak by". Houston Chronicle. 2006-11-05.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Helium+supply+deflated%3A+production+shortages+mean+some+industries+and+partygoers+must+squeak+by.&rft.date=2006-11-05&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-48"><span class="mw-cite-backlink"><b><a href="#cite_ref-48">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBrown,_David2008" class="citation web cs1">Brown, David (2008-02-02). <a rel="nofollow" class="external text" href="http://www.aapg.org/explorer/2008/02feb/helium.cfm">"Helium a New Target in New Mexico"</a>. American Association of Petroleum Geologists<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-07-15</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Helium+a+New+Target+in+New+Mexico&rft.pub=American+Association+of+Petroleum+Geologists&rft.date=2008-02-02&rft.au=Brown%2C+David&rft_id=http%3A%2F%2Fwww.aapg.org%2Fexplorer%2F2008%2F02feb%2Fhelium.cfm&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> <li id="cite_note-49"><span class="mw-cite-backlink"><b><a href="#cite_ref-49">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFVoth,_Greg2006" class="citation news cs1">Voth, Greg (2006-12-01). "Where Do We Get the Helium We Use?". The Science Teacher.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Where+Do+We+Get+the+Helium+We+Use%3F&rft.date=2006-12-01&rft.au=Voth%2C+Greg&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_1_element&action=edit&section=7" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBloch2006" class="citation book cs1">Bloch, D. R. (2006). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=yVPcSIn5xjAC"><i>Organic Chemistry Demystified</i></a>. McGraw-Hill Professional. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-07-145920-0" title="Special:BookSources/0-07-145920-0"><bdi>0-07-145920-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Organic+Chemistry+Demystified&rft.pub=McGraw-Hill+Professional&rft.date=2006&rft.isbn=0-07-145920-0&rft.au=Bloch%2C+D.+R.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DyVPcSIn5xjAC&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+1+element" class="Z3988"></span></li></ul> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output .navbox-group{white-space:nowrap;text-align:right}.mw-parser-output .navbox,.mw-parser-output .navbox-subgroup{background-color:#fdfdfd}.mw-parser-output .navbox-list{line-height:1.5em;border-color:#fdfdfd}.mw-parser-output .navbox-list-with-group{text-align:left;border-left-width:2px;border-left-style:solid}.mw-parser-output tr+tr>.navbox-abovebelow,.mw-parser-output tr+tr>.navbox-group,.mw-parser-output tr+tr>.navbox-image,.mw-parser-output tr+tr>.navbox-list{border-top:2px solid #fdfdfd}.mw-parser-output .navbox-title{background-color:#ccf}.mw-parser-output .navbox-abovebelow,.mw-parser-output .navbox-group,.mw-parser-output .navbox-subgroup .navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Periodic_table" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Periodic_table_(navbox)" title="Template:Periodic table (navbox)"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Periodic_table_(navbox)" title="Template talk:Periodic table (navbox)"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Periodic_table_(navbox)" title="Special:EditPage/Template:Periodic table (navbox)"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Periodic_table" style="font-size:114%;margin:0 4em"><a href="/wiki/Periodic_table" title="Periodic table">Periodic table</a></div></th></tr><tr><td colspan="2" class="navbox-list navbox-odd wraplinks" style="width:100%;padding:0"><div style="padding:0 0.25em"> <table style="table-layout:fixed; width:100%;" aria-describedby="periodic-table-legend"> <tbody><tr> <td style="line-height:100%;"> </td> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Alkali_metal" title="Alkali metal">1</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal">2</a> </th> <td colspan="14"> </td> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Group_3_element" title="Group 3 element">3</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Group_4_element" title="Group 4 element">4</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Group_5_element" title="Group 5 element">5</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Group_6_element" title="Group 6 element">6</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Group_7_element" title="Group 7 element">7</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Group_8_element" title="Group 8 element">8</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Group_9_element" title="Group 9 element">9</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Group_10_element" title="Group 10 element">10</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Group_11_element" title="Group 11 element">11</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Group_12_element" title="Group 12 element">12</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Boron_group" title="Boron group">13</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Carbon_group" title="Carbon group">14</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Pnictogen" title="Pnictogen">15</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Chalcogen" title="Chalcogen">16</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Halogen" title="Halogen">17</a> </th> <th scope="col" style="background:transparent; font-weight:normal;"><a href="/wiki/Noble_gas" title="Noble gas">18</a> </th></tr> <tr> <th scope="row" style="background:transparent; font-weight:normal;"><a class="mw-selflink selflink">1</a> </th> <td title="H, Hydrogen" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Hydrogen" title="Hydrogen"><span style="display:block">H</span></a></span> </td> <td colspan="30"> </td> <td title="He, Helium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Helium" title="Helium"><span style="display:block">He</span></a></span> </td></tr> <tr> <th scope="row" style="background:transparent; font-weight:normal;"><a href="/wiki/Period_2_element" title="Period 2 element">2</a> </th> <td title="Li, Lithium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Lithium" title="Lithium"><span style="display:block">Li</span></a></span> </td> <td title="Be, Beryllium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Beryllium" title="Beryllium"><span style="display:block">Be</span></a></span> </td> <td colspan="24"> </td> <td title="B, Boron" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Boron" title="Boron"><span style="display:block">B</span></a></span> </td> <td title="C, Carbon" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Carbon" title="Carbon"><span style="display:block">C</span></a></span> </td> <td title="N, Nitrogen" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Nitrogen" title="Nitrogen"><span style="display:block">N</span></a></span> </td> <td title="O, Oxygen" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Oxygen" title="Oxygen"><span style="display:block">O</span></a></span> </td> <td title="F, Fluorine" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Fluorine" title="Fluorine"><span style="display:block">F</span></a></span> </td> <td title="Ne, Neon" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Neon" title="Neon"><span style="display:block">Ne</span></a></span> </td></tr> <tr> <th scope="row" style="background:transparent; font-weight:normal;"><a href="/wiki/Period_3_element" title="Period 3 element">3</a> </th> <td title="Na, Sodium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Sodium" title="Sodium"><span style="display:block">Na</span></a></span> </td> <td title="Mg, Magnesium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Magnesium" title="Magnesium"><span style="display:block">Mg</span></a></span> </td> <td colspan="24"> </td> <td title="Al, Aluminium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Aluminium" title="Aluminium"><span style="display:block">Al</span></a></span> </td> <td title="Si, Silicon" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Silicon" title="Silicon"><span style="display:block">Si</span></a></span> </td> <td title="P, Phosphorus" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Phosphorus" title="Phosphorus"><span style="display:block">P</span></a></span> </td> <td title="S, Sulfur" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Sulfur" title="Sulfur"><span style="display:block">S</span></a></span> </td> <td title="Cl, Chlorine" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Chlorine" title="Chlorine"><span style="display:block">Cl</span></a></span> </td> <td title="Ar, Argon" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Argon" title="Argon"><span style="display:block">Ar</span></a></span> </td></tr> <tr> <th scope="row" style="background:transparent; font-weight:normal;"><a href="/wiki/Period_4_element" title="Period 4 element">4</a> </th> <td title="K, Potassium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Potassium" title="Potassium"><span style="display:block">K</span></a></span> </td> <td title="Ca, Calcium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Calcium" title="Calcium"><span style="display:block">Ca</span></a></span> </td> <td colspan="14"> </td> <td title="Sc, Scandium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Scandium" title="Scandium"><span style="display:block">Sc</span></a></span> </td> <td title="Ti, Titanium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Titanium" title="Titanium"><span style="display:block">Ti</span></a></span> </td> <td title="V, Vanadium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Vanadium" title="Vanadium"><span style="display:block">V</span></a></span> </td> <td title="Cr, Chromium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Chromium" title="Chromium"><span style="display:block">Cr</span></a></span> </td> <td title="Mn, Manganese" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Manganese" title="Manganese"><span style="display:block">Mn</span></a></span> </td> <td title="Fe, Iron" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Iron" title="Iron"><span style="display:block">Fe</span></a></span> </td> <td title="Co, Cobalt" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Cobalt" title="Cobalt"><span style="display:block">Co</span></a></span> </td> <td title="Ni, Nickel" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Nickel" title="Nickel"><span style="display:block">Ni</span></a></span> </td> <td title="Cu, Copper" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Copper" title="Copper"><span style="display:block">Cu</span></a></span> </td> <td title="Zn, Zinc" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Zinc" title="Zinc"><span style="display:block">Zn</span></a></span> </td> <td title="Ga, Gallium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Gallium" title="Gallium"><span style="display:block">Ga</span></a></span> </td> <td title="Ge, Germanium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Germanium" title="Germanium"><span style="display:block">Ge</span></a></span> </td> <td title="As, Arsenic" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Arsenic" title="Arsenic"><span style="display:block">As</span></a></span> </td> <td title="Se, Selenium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Selenium" title="Selenium"><span style="display:block">Se</span></a></span> </td> <td title="Br, Bromine" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Bromine" title="Bromine"><span style="display:block">Br</span></a></span> </td> <td title="Kr, Krypton" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Krypton" title="Krypton"><span style="display:block">Kr</span></a></span> </td></tr> <tr> <th scope="row" style="background:transparent; font-weight:normal;"><a href="/wiki/Period_5_element" title="Period 5 element">5</a> </th> <td title="Rb, Rubidium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Rubidium" title="Rubidium"><span style="display:block">Rb</span></a></span> </td> <td title="Sr, Strontium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Strontium" title="Strontium"><span style="display:block">Sr</span></a></span> </td> <td colspan="14"> </td> <td title="Y, Yttrium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Yttrium" title="Yttrium"><span style="display:block">Y</span></a></span> </td> <td title="Zr, Zirconium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Zirconium" title="Zirconium"><span style="display:block">Zr</span></a></span> </td> <td title="Nb, Niobium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Niobium" title="Niobium"><span style="display:block">Nb</span></a></span> </td> <td title="Mo, Molybdenum" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Molybdenum" title="Molybdenum"><span style="display:block">Mo</span></a></span> </td> <td title="Tc, Technetium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Technetium" title="Technetium"><span style="display:block">Tc</span></a></span> </td> <td title="Ru, Ruthenium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Ruthenium" title="Ruthenium"><span style="display:block">Ru</span></a></span> </td> <td title="Rh, Rhodium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Rhodium" title="Rhodium"><span style="display:block">Rh</span></a></span> </td> <td title="Pd, Palladium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Palladium" title="Palladium"><span style="display:block">Pd</span></a></span> </td> <td title="Ag, Silver" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Silver" title="Silver"><span style="display:block">Ag</span></a></span> </td> <td title="Cd, Cadmium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Cadmium" title="Cadmium"><span style="display:block">Cd</span></a></span> </td> <td title="In, Indium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Indium" title="Indium"><span style="display:block">In</span></a></span> </td> <td title="Sn, Tin" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Tin" title="Tin"><span style="display:block">Sn</span></a></span> </td> <td title="Sb, Antimony" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Antimony" title="Antimony"><span style="display:block">Sb</span></a></span> </td> <td title="Te, Tellurium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Tellurium" title="Tellurium"><span style="display:block">Te</span></a></span> </td> <td title="I, Iodine" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Iodine" title="Iodine"><span style="display:block">I</span></a></span> </td> <td title="Xe, Xenon" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Xenon" title="Xenon"><span style="display:block">Xe</span></a></span> </td></tr> <tr> <th scope="row" style="background:transparent; font-weight:normal;"><a href="/wiki/Period_6_element" title="Period 6 element">6</a> </th> <td title="Cs, Caesium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Caesium" title="Caesium"><span style="display:block">Cs</span></a></span> </td> <td title="Ba, Barium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Barium" title="Barium"><span style="display:block">Ba</span></a></span> </td> <td title="La, Lanthanum" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Lanthanum" title="Lanthanum"><span style="display:block">La</span></a></span> </td> <td title="Ce, Cerium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Cerium" title="Cerium"><span style="display:block">Ce</span></a></span> </td> <td title="Pr, Praseodymium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Praseodymium" title="Praseodymium"><span style="display:block">Pr</span></a></span> </td> <td title="Nd, Neodymium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Neodymium" title="Neodymium"><span style="display:block">Nd</span></a></span> </td> <td title="Pm, Promethium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Promethium" title="Promethium"><span style="display:block">Pm</span></a></span> </td> <td title="Sm, Samarium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Samarium" title="Samarium"><span style="display:block">Sm</span></a></span> </td> <td title="Eu, Europium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Europium" title="Europium"><span style="display:block">Eu</span></a></span> </td> <td title="Gd, Gadolinium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Gadolinium" title="Gadolinium"><span style="display:block">Gd</span></a></span> </td> <td title="Tb, Terbium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Terbium" title="Terbium"><span style="display:block">Tb</span></a></span> </td> <td title="Dy, Dysprosium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Dysprosium" title="Dysprosium"><span style="display:block">Dy</span></a></span> </td> <td title="Ho, Holmium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Holmium" title="Holmium"><span style="display:block">Ho</span></a></span> </td> <td title="Er, Erbium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Erbium" title="Erbium"><span style="display:block">Er</span></a></span> </td> <td title="Tm, Thulium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Thulium" title="Thulium"><span style="display:block">Tm</span></a></span> </td> <td title="Yb, Ytterbium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Ytterbium" title="Ytterbium"><span style="display:block">Yb</span></a></span> </td> <td title="Lu, Lutetium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Lutetium" title="Lutetium"><span style="display:block">Lu</span></a></span> </td> <td title="Hf, Hafnium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Hafnium" title="Hafnium"><span style="display:block">Hf</span></a></span> </td> <td title="Ta, Tantalum" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Tantalum" title="Tantalum"><span style="display:block">Ta</span></a></span> </td> <td title="W, Tungsten" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Tungsten" title="Tungsten"><span style="display:block">W</span></a></span> </td> <td title="Re, Rhenium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Rhenium" title="Rhenium"><span style="display:block">Re</span></a></span> </td> <td title="Os, Osmium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Osmium" title="Osmium"><span style="display:block">Os</span></a></span> </td> <td title="Ir, Iridium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Iridium" title="Iridium"><span style="display:block">Ir</span></a></span> </td> <td title="Pt, Platinum" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Platinum" title="Platinum"><span style="display:block">Pt</span></a></span> </td> <td title="Au, Gold" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Gold" title="Gold"><span style="display:block">Au</span></a></span> </td> <td title="Hg, Mercury" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Mercury_(element)" title="Mercury (element)"><span style="display:block">Hg</span></a></span> </td> <td title="Tl, Thallium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Thallium" title="Thallium"><span style="display:block">Tl</span></a></span> </td> <td title="Pb, Lead" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Lead" title="Lead"><span style="display:block">Pb</span></a></span> </td> <td title="Bi, Bismuth" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Bismuth" title="Bismuth"><span style="display:block">Bi</span></a></span> </td> <td title="Po, Polonium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Polonium" title="Polonium"><span style="display:block">Po</span></a></span> </td> <td title="At, Astatine" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Astatine" title="Astatine"><span style="display:block">At</span></a></span> </td> <td title="Rn, Radon" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Radon" title="Radon"><span style="display:block">Rn</span></a></span> </td></tr> <tr> <th scope="row" style="background:transparent; font-weight:normal;"><a href="/wiki/Period_7_element" title="Period 7 element">7</a> </th> <td title="Fr, Francium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Francium" title="Francium"><span style="display:block">Fr</span></a></span> </td> <td title="Ra, Radium" style="text-align:center; background-color:#ff9999; border:none; ;"><span class="nowrap"><a href="/wiki/Radium" title="Radium"><span style="display:block">Ra</span></a></span> </td> <td title="Ac, Actinium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Actinium" title="Actinium"><span style="display:block">Ac</span></a></span> </td> <td title="Th, Thorium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Thorium" title="Thorium"><span style="display:block">Th</span></a></span> </td> <td title="Pa, Protactinium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Protactinium" title="Protactinium"><span style="display:block">Pa</span></a></span> </td> <td title="U, Uranium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Uranium" title="Uranium"><span style="display:block">U</span></a></span> </td> <td title="Np, Neptunium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Neptunium" title="Neptunium"><span style="display:block">Np</span></a></span> </td> <td title="Pu, Plutonium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Plutonium" title="Plutonium"><span style="display:block">Pu</span></a></span> </td> <td title="Am, Americium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Americium" title="Americium"><span style="display:block">Am</span></a></span> </td> <td title="Cm, Curium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Curium" title="Curium"><span style="display:block">Cm</span></a></span> </td> <td title="Bk, Berkelium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Berkelium" title="Berkelium"><span style="display:block">Bk</span></a></span> </td> <td title="Cf, Californium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Californium" title="Californium"><span style="display:block">Cf</span></a></span> </td> <td title="Es, Einsteinium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Einsteinium" title="Einsteinium"><span style="display:block">Es</span></a></span> </td> <td title="Fm, Fermium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Fermium" title="Fermium"><span style="display:block">Fm</span></a></span> </td> <td title="Md, Mendelevium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Mendelevium" title="Mendelevium"><span style="display:block">Md</span></a></span> </td> <td title="No, Nobelium" style="text-align:center; background-color:#9bff99; border:none; ;"><span class="nowrap"><a href="/wiki/Nobelium" title="Nobelium"><span style="display:block">No</span></a></span> </td> <td title="Lr, Lawrencium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Lawrencium" title="Lawrencium"><span style="display:block">Lr</span></a></span> </td> <td title="Rf, Rutherfordium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Rutherfordium" title="Rutherfordium"><span style="display:block">Rf</span></a></span> </td> <td title="Db, Dubnium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Dubnium" title="Dubnium"><span style="display:block">Db</span></a></span> </td> <td title="Sg, Seaborgium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Seaborgium" title="Seaborgium"><span style="display:block">Sg</span></a></span> </td> <td title="Bh, Bohrium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Bohrium" title="Bohrium"><span style="display:block">Bh</span></a></span> </td> <td title="Hs, Hassium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Hassium" title="Hassium"><span style="display:block">Hs</span></a></span> </td> <td title="Mt, Meitnerium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Meitnerium" title="Meitnerium"><span style="display:block">Mt</span></a></span> </td> <td title="Ds, Darmstadtium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Darmstadtium" title="Darmstadtium"><span style="display:block">Ds</span></a></span> </td> <td title="Rg, Roentgenium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Roentgenium" title="Roentgenium"><span style="display:block">Rg</span></a></span> </td> <td title="Cn, Copernicium" style="text-align:center; background-color:#99ccff; border:none; ;"><span class="nowrap"><a href="/wiki/Copernicium" title="Copernicium"><span style="display:block">Cn</span></a></span> </td> <td title="Nh, Nihonium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Nihonium" title="Nihonium"><span style="display:block">Nh</span></a></span> </td> <td title="Fl, Flerovium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Flerovium" title="Flerovium"><span style="display:block">Fl</span></a></span> </td> <td title="Mc, Moscovium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Moscovium" title="Moscovium"><span style="display:block">Mc</span></a></span> </td> <td title="Lv, Livermorium" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Livermorium" title="Livermorium"><span style="display:block">Lv</span></a></span> </td> <td title="Ts, Tennessine" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Tennessine" title="Tennessine"><span style="display:block">Ts</span></a></span> </td> <td title="Og, Oganesson" style="text-align:center; background-color:#fdff8c; border:none; ;"><span class="nowrap"><a href="/wiki/Oganesson" title="Oganesson"><span style="display:block">Og</span></a></span> </td></tr></tbody></table> </div></td></tr><tr><td colspan="2" class="navbox-list navbox-even wraplinks" style="width:100%;padding:0"><div style="padding:0 0.25em"><div role="presentation" id="periodic-table-legend" style="border: 1px solid #a2a9b1; width:100%; line-height:120%; text-align:center; vertical-align:top; background:#f8f8f8; margin:0; margin:0;"><div style="padding:0.3em;"> <table style="width:100%; line-height:1.2em; table-layout:fixed; overflow:hidden; text-align:center;"> <tbody><tr> <td style="padding:0 1px; background:#ff9999;"><a href="/wiki/S-block" class="mw-redirect" title="S-block">s-block</a> </td> <td style="padding:0 1px; background:#9bff99;"><a href="/wiki/F-block" class="mw-redirect" title="F-block">f-block</a> </td> <td style="padding:0 1px; background:#99ccff;"><a href="/wiki/D-block" class="mw-redirect" title="D-block">d-block</a> </td> <td style="padding:0 1px; background:#fdff8c;"><a href="/wiki/P-block" class="mw-redirect" title="P-block">p-block</a> </td></tr></tbody></table> </div> </div></div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Periodic_table" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Navbox_periodic_table" title="Template:Navbox periodic table"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Navbox_periodic_table" title="Template talk:Navbox periodic table"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Navbox_periodic_table" title="Special:EditPage/Template:Navbox periodic table"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Periodic_table" style="font-size:114%;margin:0 4em"><a href="/wiki/Periodic_table" title="Periodic table">Periodic table</a></div></th></tr><tr><th scope="row" class="navbox-group wraplinks" style="width:1%;white-space: normal !important;">Periodic table forms</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Types_of_periodic_tables" title="Types of periodic tables">Alternatives</a></li> <li><a href="/wiki/Extended_periodic_table" title="Extended periodic table">Extended periodic table</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group wraplinks" style="width:1%;white-space: normal !important;"><a href="/wiki/Names_for_sets_of_chemical_elements" title="Names for sets of chemical elements">Sets of elements</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%;white-space: normal !important;">By periodic table structure</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Group_(periodic_table)" title="Group (periodic table)">Groups</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Alkali_metal" title="Alkali metal">1 (Hydrogen and alkali metals)</a></li> <li><a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal">2 (Alkaline earth metals)</a></li> <li><a href="/wiki/Group_3_element" title="Group 3 element">3</a></li> <li><a href="/wiki/Group_4_element" title="Group 4 element">4</a></li> <li><a href="/wiki/Group_5_element" title="Group 5 element">5</a></li> <li><a href="/wiki/Group_6_element" title="Group 6 element">6</a></li> <li><a href="/wiki/Group_7_element" title="Group 7 element">7</a></li> <li><a href="/wiki/Group_8_element" title="Group 8 element">8</a></li> <li><a href="/wiki/Group_9_element" title="Group 9 element">9</a></li> <li><a href="/wiki/Group_10_element" title="Group 10 element">10</a></li> <li><a href="/wiki/Group_11_element" title="Group 11 element">11</a></li> <li><a href="/wiki/Group_12_element" title="Group 12 element">12</a></li> <li><a href="/wiki/Boron_group" title="Boron group">13 (Triels)</a></li> <li><a href="/wiki/Carbon_group" title="Carbon group">14 (Tetrels)</a></li> <li><a href="/wiki/Pnictogen" title="Pnictogen">15 (Pnictogens)</a></li> <li><a href="/wiki/Chalcogen" title="Chalcogen">16 (Chalcogens)</a></li> <li><a href="/wiki/Halogen" title="Halogen">17 (Halogens)</a></li> <li><a href="/wiki/Noble_gas" title="Noble gas">18 (Noble gases)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Period_(periodic_table)" title="Period (periodic table)">Periods</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a class="mw-selflink selflink">1</a></li> <li><a href="/wiki/Period_2_element" title="Period 2 element">2</a></li> <li><a href="/wiki/Period_3_element" title="Period 3 element">3</a></li> <li><a href="/wiki/Period_4_element" title="Period 4 element">4</a></li> <li><a href="/wiki/Period_5_element" title="Period 5 element">5</a></li> <li><a href="/wiki/Period_6_element" title="Period 6 element">6</a></li> <li><a href="/wiki/Period_7_element" title="Period 7 element">7</a></li> <li><a href="/wiki/Extended_periodic_table" title="Extended periodic table">8+</a> <ul><li><a href="/wiki/Extended_periodic_table#Aufbau_model" title="Extended periodic table">Aufbau</a></li> <li><a href="/wiki/Extended_periodic_table#Fricke" title="Extended periodic table">Fricke</a></li> <li><a href="/wiki/Extended_periodic_table#Pyykkö" title="Extended periodic table">Pyykkö</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Block_(periodic_table)" title="Block (periodic table)">Blocks</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aufbau_principle" title="Aufbau principle">Aufbau principle</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;white-space: normal !important;">By <a href="/wiki/Properties_of_metals,_metalloids_and_nonmetals" title="Properties of metals, metalloids and nonmetals">metallicity</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Metal" title="Metal">Metals</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Lanthanide" title="Lanthanide">Lanthanides</a></li> <li><a href="/wiki/Actinide" title="Actinide">Actinides</a></li> <li><a href="/wiki/Transition_metal" title="Transition metal">Transition metals</a></li> <li><a href="/wiki/Post-transition_metal" title="Post-transition metal">Post-transition metals</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Metalloid" title="Metalloid">Metalloids</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Lists_of_metalloids" title="Lists of metalloids">Lists of metalloids by source</a></li> <li><a href="/wiki/Dividing_line_between_metals_and_nonmetals" title="Dividing line between metals and nonmetals">Dividing line</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Nonmetal" title="Nonmetal">Nonmetals</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Noble_gas" title="Noble gas">Noble gases</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;white-space: normal !important;">Other sets</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Platinum_group" title="Platinum group">Platinum-group metals (PGM)</a></li> <li><a href="/wiki/Rare-earth_element" title="Rare-earth element">Rare-earth elements</a></li> <li><a href="/wiki/Refractory_metals" title="Refractory metals">Refractory metals</a></li> <li><a href="/wiki/Precious_metal" title="Precious metal">Precious metals</a></li> <li><a href="/wiki/Coinage_metals" title="Coinage metals">Coinage metals</a></li> <li><a href="/wiki/Noble_metal" title="Noble metal">Noble metals</a></li> <li><a href="/wiki/Heavy_metal_element" title="Heavy metal element">Heavy metals</a></li> <li><a href="/wiki/Native_metal" title="Native metal">Native metals</a></li> <li><a href="/wiki/Transuranium_element" title="Transuranium element">Transuranium elements</a></li> <li><a href="/wiki/Superheavy_element" title="Superheavy element">Superheavy elements</a></li> <li><a href="/wiki/Major_actinide" title="Major actinide">Major actinides</a></li> <li><a href="/wiki/Minor_actinide" title="Minor actinide">Minor actinides</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group wraplinks" style="width:1%;white-space: normal !important;"><a href="/wiki/Chemical_element" title="Chemical element">Elements</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%;white-space: normal;"><a href="/wiki/List_of_chemical_elements" title="List of chemical elements">Lists</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li>By: <a href="/wiki/Abundance_of_the_chemical_elements" title="Abundance of the chemical elements">Abundance</a> (<a href="/wiki/Composition_of_the_human_body" title="Composition of the human body">in humans</a>)</li> <li><a href="/wiki/List_of_elements_by_atomic_properties" title="List of elements by atomic properties">Atomic properties</a></li> <li><a href="/wiki/List_of_elements_by_stability_of_isotopes" title="List of elements by stability of isotopes">Nuclear stability</a></li> <li><a href="/wiki/Chemical_symbol" title="Chemical symbol">Symbol</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;white-space: normal;"><a href="/wiki/Chemical_element#Properties" title="Chemical element">Properties</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/List_of_aqueous_ions_by_element" title="List of aqueous ions by element">Aqueous chemistry</a></li> <li><a href="/wiki/Periodic_table_(crystal_structure)" title="Periodic table (crystal structure)">Crystal structure</a></li> <li><a href="/wiki/Periodic_table_(electron_configurations)" title="Periodic table (electron configurations)">Electron configuration</a></li> <li><a href="/wiki/Electronegativity" title="Electronegativity">Electronegativity</a></li> <li><a href="/wiki/Goldschmidt_classification" title="Goldschmidt classification">Goldschmidt classification</a></li> <li><a href="/wiki/Term_symbol" title="Term symbol">Term symbol</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;white-space: normal;">Data pages</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Abundances_of_the_elements_(data_page)" title="Abundances of the elements (data page)">Abundance</a></li> <li><a href="/wiki/Atomic_radii_of_the_elements_(data_page)" title="Atomic radii of the elements (data page)">Atomic radius</a></li> <li><a href="/wiki/Boiling_points_of_the_elements_(data_page)" title="Boiling points of the elements (data page)">Boiling point</a></li> <li><a href="/wiki/Critical_points_of_the_elements_(data_page)" title="Critical points of the elements (data page)">Critical point</a></li> <li><a href="/wiki/Densities_of_the_elements_(data_page)" title="Densities of the elements (data page)">Density</a></li> <li><a href="/wiki/Elastic_properties_of_the_elements_(data_page)" title="Elastic properties of the elements (data page)">Elasticity</a></li> <li><a href="/wiki/Electrical_resistivities_of_the_elements_(data_page)" title="Electrical resistivities of the elements (data page)">Electrical resistivity</a></li> <li><a href="/wiki/Electron_affinity_(data_page)" title="Electron affinity (data page)">Electron affinity</a></li> <li><a href="/wiki/Electron_configurations_of_the_elements_(data_page)" title="Electron configurations of the elements (data page)">Electron configuration</a></li> <li><a href="/wiki/Electronegativities_of_the_elements_(data_page)" title="Electronegativities of the elements (data page)">Electronegativity</a></li> <li><a href="/wiki/Hardnesses_of_the_elements_(data_page)" title="Hardnesses of the elements (data page)">Hardness</a></li> <li><a href="/wiki/Heat_capacities_of_the_elements_(data_page)" title="Heat capacities of the elements (data page)">Heat capacity</a></li> <li><a href="/wiki/Heats_of_fusion_of_the_elements_(data_page)" title="Heats of fusion of the elements (data page)">Heat of fusion</a></li> <li><a href="/wiki/Heats_of_vaporization_of_the_elements_(data_page)" title="Heats of vaporization of the elements (data page)">Heat of vaporization</a></li> <li><a href="/wiki/Ionization_energies_of_the_elements_(data_page)" title="Ionization energies of the elements (data page)">Ionization energy</a></li> <li><a href="/wiki/Melting_points_of_the_elements_(data_page)" title="Melting points of the elements (data page)">Melting point</a></li> <li><a href="/wiki/Oxidation_state" title="Oxidation state">Oxidation state</a></li> <li><a href="/wiki/Speeds_of_sound_of_the_elements" title="Speeds of sound of the elements">Speed of sound</a></li> <li><a href="/wiki/Thermal_conductivities_of_the_elements_(data_page)" title="Thermal conductivities of the elements (data page)">Thermal conductivity</a></li> <li><a href="/wiki/Thermal_expansivities_of_the_elements" title="Thermal expansivities of the elements">Thermal expansion coefficient</a></li> <li><a href="/wiki/Vapor_pressures_of_the_elements_(data_page)" title="Vapor pressures of the elements (data page)">Vapor pressure</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group wraplinks" style="width:1%;white-space: normal !important;"><a href="/wiki/History_of_the_periodic_table" title="History of the periodic table">History</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Discovery_of_chemical_elements" title="Discovery of chemical elements">Element discoveries</a> <ul><li><a href="/wiki/Dmitri_Mendeleev" title="Dmitri Mendeleev">Dmitri Mendeleev</a></li> <li><a href="/wiki/Dmitri_Mendeleev#Periodic_table" title="Dmitri Mendeleev">1871 table</a></li> <li><a href="/wiki/Mendeleev%27s_predicted_elements" title="Mendeleev's predicted elements">1869 predictions</a></li></ul></li> <li><a href="/wiki/Naming_of_chemical_elements" title="Naming of chemical elements">Naming</a> <ul><li><a href="/wiki/List_of_chemical_element_name_etymologies" title="List of chemical element name etymologies">etymology</a></li> <li><a href="/wiki/List_of_chemical_element_naming_controversies" title="List of chemical element naming controversies">controversies</a></li> <li><a href="/wiki/List_of_chemical_elements_named_after_places" title="List of chemical elements named after places">for places</a></li> <li><a href="/wiki/List_of_chemical_elements_named_after_people" title="List of chemical elements named after people">for people</a></li> <li><a href="/wiki/Chemical_elements_in_East_Asian_languages" title="Chemical elements in East Asian languages">in East Asian languages</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group wraplinks" style="width:1%;white-space: normal !important;">See also</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/International_Union_of_Pure_and_Applied_Chemistry" title="International Union of Pure and Applied Chemistry">IUPAC</a> <ul><li><a href="/wiki/Chemical_nomenclature" title="Chemical nomenclature">nomenclature</a></li> <li><a href="/wiki/Systematic_element_name" title="Systematic element name">systematic element name</a></li></ul></li> <li><a href="/wiki/Trivial_name" title="Trivial name">Trivial name</a></li> <li><a href="/wiki/Dmitri_Mendeleev" title="Dmitri Mendeleev">Dmitri Mendeleev</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> 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