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<li id="toc-Period_1" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Period_1"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>Period 1</span> </div> </a> <ul id="toc-Period_1-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Period_2" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Period_2"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.2</span> <span>Period 2</span> </div> </a> <ul id="toc-Period_2-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Period_3" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Period_3"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.3</span> <span>Period 3</span> </div> </a> <ul id="toc-Period_3-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Period_4" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Period_4"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.4</span> <span>Period 4</span> </div> </a> <ul id="toc-Period_4-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Period_5" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Period_5"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.5</span> <span>Period 5</span> </div> </a> <ul id="toc-Period_5-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Period_6" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Period_6"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.6</span> <span>Period 6</span> </div> </a> <ul id="toc-Period_6-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Period_7" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Period_7"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.7</span> <span>Period 7</span> </div> </a> <ul id="toc-Period_7-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Period_8" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Period_8"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.8</span> <span>Period 8</span> </div> </a> <ul id="toc-Period_8-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>References</span> </div> </a> <ul id="toc-References-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 mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Period (periodic table)</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 81 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-81" 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">81 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Periode_(periodieke_tabel)" title="Periode (periodieke tabel) – Afrikaans" lang="af" hreflang="af" data-title="Periode (periodieke tabel)" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-smn mw-list-item"><a href="https://smn.wikipedia.org/wiki/R%C3%A1i%C4%91u_(r%C3%A1i%C4%91ul%C3%A2%C5%A1_vu%C3%A1h%C3%A1d%C3%A2h)" title="Ráiđu (ráiđulâš vuáhádâh) – Inari Sami" lang="smn" hreflang="smn" data-title="Ráiđu (ráiđulâš vuáhádâh)" data-language-autonym="Anarâškielâ" data-language-local-name="Inari Sami" class="interlanguage-link-target"><span>Anarâškielâ</span></a></li><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_%E0%A4%B8%E0%A4%BE%E0%A4%B0%E0%A4%A3%E0%A5%80_%E0%A4%86%E0%A4%B5%E0%A4%B0%E0%A5%8D%E0%A4%A4" title="आवर्त सारणी आवर्त – Angika" lang="anp" hreflang="anp" data-title="आवर्त सारणी आवर्त" 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%AF%D9%88%D8%B1%D8%A9_(%D8%AC%D8%AF%D9%88%D9%84_%D8%AF%D9%88%D8%B1%D9%8A)" title="دورة (جدول دوري) – Arabic" lang="ar" hreflang="ar" data-title="دورة (جدول دوري)" 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/Periodo_d%27a_tabla_periodica" title="Periodo d'a tabla periodica – Aragonese" lang="an" hreflang="an" data-title="Periodo d'a tabla periodica" 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/Periodu_de_la_tabla_peri%C3%B3dica" title="Periodu de la tabla periódica – Asturian" lang="ast" hreflang="ast" data-title="Periodu de la tabla periódica" 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_c%C9%99dv%C9%99l_d%C3%B6vr%C3%BC" title="Dövri cədvəl dövrü – Azerbaijani" lang="az" hreflang="az" data-title="Dövri cədvəl dövrü" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-ban mw-list-item"><a href="https://ban.wikipedia.org/wiki/P%C3%A9riode_(tab%C3%A9l_p%C3%A9riodik)" title="Période (tabél périodik) – Balinese" lang="ban" hreflang="ban" data-title="Période (tabél périodik)" data-language-autonym="Basa Bali" data-language-local-name="Balinese" class="interlanguage-link-target"><span>Basa Bali</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AA%E0%A6%B0%E0%A7%8D%E0%A6%AF%E0%A6%BE%E0%A6%AF%E0%A6%BC_(%E0%A6%AA%E0%A6%B0%E0%A7%8D%E0%A6%AF%E0%A6%BE%E0%A6%AF%E0%A6%BC_%E0%A6%B8%E0%A6%BE%E0%A6%B0%E0%A6%A3%E0%A6%BF)" title="পর্যায় (পর্যায় সারণি) – Bangla" lang="bn" hreflang="bn" data-title="পর্যায় (পর্যায় সারণি)" 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/Go%C3%A2n-s%C3%B2%CD%98_%C3%AA_chiu-k%C3%AE" title="Goân-sò͘ ê chiu-kî – Minnan" lang="nan" hreflang="nan" data-title="Goân-sò͘ ê chiu-kî" 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-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%9F%D0%B5%D1%80%D1%8B%D1%8F%D0%B4_%D0%BF%D0%B5%D1%80%D1%8B%D1%8F%D0%B4%D1%8B%D1%87%D0%BD%D0%B0%D0%B9_%D1%81%D1%96%D1%81%D1%82%D1%8D%D0%BC%D1%8B" title="Перыяд перыядычнай сістэмы – Belarusian" lang="be" hreflang="be" data-title="Перыяд перыядычнай сістэмы" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</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_%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 на периодичната система – Bulgarian" lang="bg" hreflang="bg" data-title="Период 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-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Perioda_periodnog_sistema_elemenata" title="Perioda periodnog sistema elemenata – Bosnian" lang="bs" hreflang="bs" data-title="Perioda periodnog sistema elemenata" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-br mw-list-item"><a href="https://br.wikipedia.org/wiki/Trovezh_(taolenn_drovezhiek)" title="Trovezh (taolenn drovezhiek) – Breton" lang="br" hreflang="br" data-title="Trovezh (taolenn drovezhiek)" data-language-autonym="Brezhoneg" data-language-local-name="Breton" class="interlanguage-link-target"><span>Brezhoneg</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Per%C3%ADode_de_la_taula_peri%C3%B2dica" title="Període de la taula periòdica – Catalan" lang="ca" hreflang="ca" data-title="Període de la taula periòdica" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cv mw-list-item"><a href="https://cv.wikipedia.org/wiki/%D0%9F%D0%B5%D1%80%D0%B8%D0%BE%D0%B4_(%D1%85%D0%B8%D0%BC%D0%B8)" title="Период (хими) – Chuvash" lang="cv" hreflang="cv" data-title="Период (хими)" data-language-autonym="Чӑвашла" data-language-local-name="Chuvash" class="interlanguage-link-target"><span>Чӑвашла</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Perioda_(periodick%C3%A1_tabulka)" title="Perioda (periodická tabulka) – Czech" lang="cs" hreflang="cs" data-title="Perioda (periodická tabulka)" 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/Cyfnod_y_tabl_cyfnodol" title="Cyfnod y tabl cyfnodol – Welsh" lang="cy" hreflang="cy" data-title="Cyfnod y tabl cyfnodol" 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_(periodiske_system)" title="Periode (periodiske system) – Danish" lang="da" hreflang="da" data-title="Periode (periodiske system)" 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/Periode_des_Periodensystems" title="Periode des Periodensystems – German" lang="de" hreflang="de" data-title="Periode des Periodensystems" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Periood_(keemia)" title="Periood (keemia) – Estonian" lang="et" hreflang="et" data-title="Periood (keemia)" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%A0%CE%B5%CF%81%CE%AF%CE%BF%CE%B4%CE%BF%CF%82_(%CF%80%CE%B5%CF%81%CE%B9%CE%BF%CE%B4%CE%B9%CE%BA%CE%BF%CF%8D_%CF%80%CE%AF%CE%BD%CE%B1%CE%BA%CE%B1)" title="Περίοδος (περιοδικού πίνακα) – Greek" lang="el" hreflang="el" data-title="Περίοδος (περιοδικού πίνακα)" 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-Q70893996 mw-list-item" title=""><a href="https://es.wikipedia.org/wiki/Periodo_de_la_tabla_peri%C3%B3dica" title="Periodo de la tabla periódica – Spanish" lang="es" hreflang="es" data-title="Periodo de la tabla periódica" 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/Periodo_de_la_perioda_tabelo" title="Periodo de la perioda tabelo – Esperanto" lang="eo" hreflang="eo" data-title="Periodo de la perioda tabelo" 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/Taula_periodikoko_periodo" title="Taula periodikoko periodo – Basque" lang="eu" hreflang="eu" data-title="Taula periodikoko periodo" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%AF%D9%88%D8%B1%D9%87_(%D8%AC%D8%AF%D9%88%D9%84_%D8%AA%D9%86%D8%A7%D9%88%D8%A8%DB%8C)" title="دوره (جدول تناوبی) – Persian" lang="fa" hreflang="fa" data-title="دوره (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_du_tableau_p%C3%A9riodique" title="Période du tableau périodique – French" lang="fr" hreflang="fr" data-title="Période 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_(Skiekunde)" title="Perioade (Skiekunde) – Western Frisian" lang="fy" hreflang="fy" data-title="Perioade (Skiekunde)" data-language-autonym="Frysk" data-language-local-name="Western Frisian" class="interlanguage-link-target"><span>Frysk</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Per%C3%ADodo_da_t%C3%A1boa_peri%C3%B3dica" title="Período da táboa periódica – Galician" lang="gl" hreflang="gl" data-title="Período da táboa periódica" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EC%A3%BC%EA%B8%B0_(%EC%A3%BC%EA%B8%B0%EC%9C%A8%ED%91%9C)" title="주기 (주기율표) – Korean" lang="ko" hreflang="ko" data-title="주기 (주기율표)" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%8A%D5%A1%D6%80%D5%A2%D5%A5%D6%80%D5%B8%D6%82%D5%A9%D5%B5%D5%B8%D6%82%D5%B6_(%D6%84%D5%AB%D5%B4%D5%AB%D5%A1)" title="Պարբերություն (քիմիա) – Armenian" lang="hy" hreflang="hy" data-title="Պարբերություն (քիմիա)" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%86%E0%A4%B5%E0%A4%B0%E0%A5%8D%E0%A4%A4_(%E0%A4%86%E0%A4%B5%E0%A4%B0%E0%A5%8D%E0%A4%A4_%E0%A4%B8%E0%A4%BE%E0%A4%B0%E0%A4%A3%E0%A5%80)" title="आवर्त (आवर्त सारणी) – Hindi" lang="hi" hreflang="hi" data-title="आवर्त (आवर्त सारणी)" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Perioda_periodnog_sustava" title="Perioda periodnog sustava – Croatian" lang="hr" hreflang="hr" data-title="Perioda periodnog sustava" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Periode_tabel_periodik" title="Periode tabel periodik – Indonesian" lang="id" hreflang="id" data-title="Periode tabel periodik" 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/Periodos_del_tabella_periodic" title="Periodos del tabella periodic – Interlingua" lang="ia" hreflang="ia" data-title="Periodos del tabella periodic" data-language-autonym="Interlingua" data-language-local-name="Interlingua" class="interlanguage-link-target"><span>Interlingua</span></a></li><li class="interlanguage-link interwiki-is mw-list-item"><a href="https://is.wikipedia.org/wiki/Lota_(lotukerfi%C3%B0)" title="Lota (lotukerfið) – Icelandic" lang="is" hreflang="is" data-title="Lota (lotukerfið)" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target"><span>Íslenska</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Periodo_della_tavola_periodica" title="Periodo della tavola periodica – Italian" lang="it" hreflang="it" data-title="Periodo della tavola periodica" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%9E%D7%97%D7%96%D7%95%D7%A8_(%D7%9B%D7%99%D7%9E%D7%99%D7%94)" title="מחזור (כימיה) – Hebrew" lang="he" hreflang="he" data-title="מחזור (כימיה)" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-jv mw-list-item"><a href="https://jv.wikipedia.org/wiki/P%C3%A9riode_tab%C3%A8l_p%C3%A9riodik" title="Période tabèl périodik – Javanese" lang="jv" hreflang="jv" data-title="Période tabèl périodik" data-language-autonym="Jawa" data-language-local-name="Javanese" class="interlanguage-link-target"><span>Jawa</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%9E%E1%83%94%E1%83%A0%E1%83%98%E1%83%9D%E1%83%93%E1%83%98_(%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%90)" title="პერიოდი (პერიოდული სისტემა) – Georgian" lang="ka" hreflang="ka" data-title="პერიოდი (პერიოდული სისტემა)" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-ht mw-list-item"><a href="https://ht.wikipedia.org/wiki/Pery%C3%B2d_(chimi)" title="Peryòd (chimi) – Haitian Creole" lang="ht" hreflang="ht" data-title="Peryòd (chimi)" data-language-autonym="Kreyòl ayisyen" data-language-local-name="Haitian Creole" class="interlanguage-link-target"><span>Kreyòl ayisyen</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Periodus_(systema_periodicum)" title="Periodus (systema periodicum) – Latin" lang="la" hreflang="la" data-title="Periodus (systema periodicum)" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Periodisk%C4%81s_tabulas_periods" title="Periodiskās tabulas periods – Latvian" lang="lv" hreflang="lv" data-title="Periodiskās tabulas periods" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lmo mw-list-item"><a href="https://lmo.wikipedia.org/wiki/Period_de_la_taola_peri%C3%B2dica" title="Period de la taola periòdica – Lombard" lang="lmo" hreflang="lmo" data-title="Period de la taola periòdica" data-language-autonym="Lombard" data-language-local-name="Lombard" class="interlanguage-link-target"><span>Lombard</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Peri%C3%B3dusos_rendszerbeli_peri%C3%B3dus" title="Periódusos rendszerbeli periódus – Hungarian" lang="hu" hreflang="hu" data-title="Periódusos rendszerbeli periódus" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%9F%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D0%B0_(%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D0%B5%D0%BD_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC)" title="Периода (периоден систем) – Macedonian" lang="mk" hreflang="mk" data-title="Периода (периоден 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%AA%E0%B5%80%E0%B4%B0%E0%B5%80%E0%B4%A1%E0%B5%8D_(%E0%B4%86%E0%B4%B5%E0%B5%BC%E0%B4%A4%E0%B5%8D%E0%B4%A4%E0%B4%A8%E0%B4%AA%E0%B5%8D%E0%B4%AA%E0%B4%9F%E0%B5%8D%E0%B4%9F%E0%B4%BF%E0%B4%95)" title="പീരീഡ് (ആവർത്തനപ്പട്ടിക) – Malayalam" lang="ml" hreflang="ml" data-title="പീരീഡ് (ആവർത്തനപ്പട്ടിക)" 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/Kala_jadual_berkala" title="Kala jadual berkala – Malay" lang="ms" hreflang="ms" data-title="Kala jadual berkala" 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-mn mw-list-item"><a href="https://mn.wikipedia.org/wiki/%D2%AE%D0%B5%D0%BB%D1%8D%D1%85_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B8%D0%B9%D0%BD_%D2%AF%D0%B5" title="Үелэх системийн үе – Mongolian" lang="mn" hreflang="mn" data-title="Үелэх системийн үе" data-language-autonym="Монгол" data-language-local-name="Mongolian" class="interlanguage-link-target"><span>Монгол</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Periode_(scheikunde)" title="Periode (scheikunde) – Dutch" lang="nl" hreflang="nl" data-title="Periode (scheikunde)" 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/%E5%85%83%E7%B4%A0%E3%81%AE%E5%91%A8%E6%9C%9F" title="元素の周期 – Japanese" lang="ja" hreflang="ja" data-title="元素の周期" 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-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Periodesystemets_perioder" title="Periodesystemets perioder – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Periodesystemets perioder" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Periodane_i_periodesystemet" title="Periodane i periodesystemet – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Periodane i periodesystemet" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-or mw-list-item"><a href="https://or.wikipedia.org/wiki/%E0%AC%AA%E0%AC%B0%E0%AD%8D%E0%AC%AF%E0%AD%8D%E0%AD%9F%E0%AC%BE%E0%AD%9F_(%E0%AC%AA%E0%AC%B0%E0%AD%8D%E0%AC%AF%E0%AD%8D%E0%AD%9F%E0%AC%BE%E0%AD%9F_%E0%AC%B8%E0%AC%BE%E0%AC%B0%E0%AC%A3%E0%AD%80)" title="ପର୍ଯ୍ୟାୟ (ପର୍ଯ୍ୟାୟ ସାରଣୀ) – Odia" lang="or" hreflang="or" data-title="ପର୍ଯ୍ୟାୟ (ପର୍ଯ୍ୟାୟ ସାରଣୀ)" data-language-autonym="ଓଡ଼ିଆ" data-language-local-name="Odia" class="interlanguage-link-target"><span>ଓଡ଼ିଆ</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%A9%80%E0%A8%85%E0%A8%A1_(%E0%A8%AE%E0%A8%BF%E0%A8%86%E0%A8%A6%E0%A9%80_%E0%A8%AA%E0%A8%B9%E0%A8%BE%E0%A9%9C%E0%A8%BE)" title="ਪੀਰੀਅਡ (ਮਿਆਦੀ ਪਹਾੜਾ) – Punjabi" lang="pa" hreflang="pa" data-title="ਪੀਰੀਅਡ (ਮਿਆਦੀ ਪਹਾੜਾ)" data-language-autonym="ਪੰਜਾਬੀ" data-language-local-name="Punjabi" class="interlanguage-link-target"><span>ਪੰਜਾਬੀ</span></a></li><li class="interlanguage-link interwiki-nds mw-list-item"><a href="https://nds.wikipedia.org/wiki/Periood_(Chemie)" title="Periood (Chemie) – Low German" lang="nds" hreflang="nds" data-title="Periood (Chemie)" data-language-autonym="Plattdüütsch" data-language-local-name="Low German" class="interlanguage-link-target"><span>Plattdüütsch</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Per%C3%ADodo_(qu%C3%ADmica)" title="Período (química) – Portuguese" lang="pt" hreflang="pt" data-title="Período (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/Perioad%C4%83_(tabelul_periodic_al_elementelor)" title="Perioadă (tabelul periodic al elementelor) – Romanian" lang="ro" hreflang="ro" data-title="Perioadă (tabelul periodic al elementelor)" 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%B8%D0%BE%D0%B4_(%D1%85%D0%B8%D0%BC%D0%B8%D1%8F)" title="Период (химия) – Russian" lang="ru" hreflang="ru" data-title="Период (химия)" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Period_(periodic_table)" title="Period (periodic table) – Simple English" lang="en-simple" hreflang="en-simple" data-title="Period (periodic table)" 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/Peri%C3%B3da_(periodick%C3%A1_tabu%C4%BEka)" title="Perióda (periodická tabuľka) – Slovak" lang="sk" hreflang="sk" data-title="Perióda (periodická tabuľka)" 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/Perioda_periodnega_sistema" title="Perioda periodnega sistema – Slovenian" lang="sl" hreflang="sl" data-title="Perioda periodnega sistema" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-so mw-list-item"><a href="https://so.wikipedia.org/wiki/Walxaha" title="Walxaha – Somali" lang="so" hreflang="so" data-title="Walxaha" data-language-autonym="Soomaaliga" data-language-local-name="Somali" class="interlanguage-link-target"><span>Soomaaliga</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%9F%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D0%B0_(%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4%D0%BD%D0%B8_%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC)" title="Периода (периодни систем) – Serbian" lang="sr" hreflang="sr" data-title="Периода (периодни систем)" 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/Perioda_periodnog_sistema_elemenata" title="Perioda periodnog sistema elemenata – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Perioda periodnog sistema elemenata" 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-su mw-list-item"><a href="https://su.wikipedia.org/wiki/Periode_tab%C3%A9l_periodik" title="Periode tabél periodik – Sundanese" lang="su" hreflang="su" data-title="Periode tabél periodik" data-language-autonym="Sunda" data-language-local-name="Sundanese" class="interlanguage-link-target"><span>Sunda</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Jakso_(jaksollinen_j%C3%A4rjestelm%C3%A4)" title="Jakso (jaksollinen järjestelmä) – Finnish" lang="fi" hreflang="fi" data-title="Jakso (jaksollinen järjestelmä)" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Periodiska_systemets_perioder" title="Periodiska systemets perioder – Swedish" lang="sv" hreflang="sv" data-title="Periodiska systemets perioder" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</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%B5%E0%AE%B0%E0%AE%BF%E0%AE%9A%E0%AF%88_(%E0%AE%A4%E0%AE%A9%E0%AE%BF%E0%AE%AE_%E0%AE%85%E0%AE%9F%E0%AF%8D%E0%AE%9F%E0%AE%B5%E0%AE%A3%E0%AF%88)" title="கிடை வரிசை (தனிம அட்டவணை) – Tamil" lang="ta" hreflang="ta" data-title="கிடை வரிசை (தனிம அட்டவணை)" 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_(%E0%B0%86%E0%B0%B5%E0%B0%B0%E0%B1%8D%E0%B0%A4%E0%B0%A8_%E0%B0%AA%E0%B0%9F%E0%B1%8D%E0%B0%9F%E0%B0%BF%E0%B0%95)" title="పీరియడ్ (ఆవర్తన పట్టిక) – Telugu" lang="te" hreflang="te" data-title="పీరియడ్ (ఆవర్తన పట్టిక)" 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%84%E0%B8%B2%E0%B8%9A_(%E0%B8%95%E0%B8%B2%E0%B8%A3%E0%B8%B2%E0%B8%87%E0%B8%98%E0%B8%B2%E0%B8%95%E0%B8%B8)" title="คาบ (ตารางธาตุ) – Thai" lang="th" hreflang="th" data-title="คาบ (ตารางธาตุ)" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tg mw-list-item"><a href="https://tg.wikipedia.org/wiki/%D0%94%D0%B0%D0%B2%D1%80%D0%B0_(%D0%BA%D0%B8%D0%BC%D0%B8%D1%91)" title="Давра (кимиё) – Tajik" lang="tg" hreflang="tg" data-title="Давра (кимиё)" data-language-autonym="Тоҷикӣ" data-language-local-name="Tajik" class="interlanguage-link-target"><span>Тоҷикӣ</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Periyot_(periyodik_tablo)" title="Periyot (periyodik tablo) – Turkish" lang="tr" hreflang="tr" data-title="Periyot (periyodik tablo)" 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_%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" title="Період періодичної системи – Ukrainian" lang="uk" hreflang="uk" data-title="Період 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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">Method of visualizing the relationship between elements</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Simple_Periodic_Table_Chart-blocks.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/03/Simple_Periodic_Table_Chart-blocks.svg/410px-Simple_Periodic_Table_Chart-blocks.svg.png" decoding="async" width="410" height="217" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/03/Simple_Periodic_Table_Chart-blocks.svg/615px-Simple_Periodic_Table_Chart-blocks.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/03/Simple_Periodic_Table_Chart-blocks.svg/820px-Simple_Periodic_Table_Chart-blocks.svg.png 2x" data-file-width="1205" data-file-height="638" /></a><figcaption>In the <a href="/wiki/Periodic_table" title="Periodic table">periodic table</a> of the elements, each numbered row is a period.</figcaption></figure> <p>A <b>period</b> on the <a href="/wiki/Periodic_table" title="Periodic table">periodic table</a> is a row of <a href="/wiki/Chemical_element" title="Chemical element">chemical elements</a>. All <a href="/wiki/Chemical_element" title="Chemical element">elements</a> in a row have the same number of <a href="/wiki/Electron_shells" class="mw-redirect" title="Electron shells">electron shells</a>. Each next element in a period has one more <a href="/wiki/Proton" title="Proton">proton</a> and is less <a href="/wiki/Metal" title="Metal">metallic</a> than its predecessor. Arranged this way, elements in the same <a href="/wiki/Group_(periodic_table)" title="Group (periodic table)">group</a> (column) have similar <a href="/wiki/Chemical_property" title="Chemical property">chemical</a> and <a href="/wiki/Physical_property" title="Physical property">physical properties</a>, reflecting the <a href="/wiki/Periodic_law" class="mw-redirect" title="Periodic law">periodic law</a>. For example, the halogens lie in the second-to-last group (<a href="/wiki/Halogen" title="Halogen">group 17</a>) and share similar properties, such as high reactivity and the tendency to gain one electron to arrive at a noble-gas electronic configuration. As of 2022<sup class="plainlinks noexcerpt noprint asof-tag update" style="display:none;"><a class="external text" href="https://en.wikipedia.org/w/index.php?title=Period_(periodic_table)&action=edit">[update]</a></sup>, a total of 118 elements have been discovered and confirmed. </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Madelung_rule.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/02/Madelung_rule.svg/260px-Madelung_rule.svg.png" decoding="async" width="260" height="293" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/02/Madelung_rule.svg/390px-Madelung_rule.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/02/Madelung_rule.svg/520px-Madelung_rule.svg.png 2x" data-file-width="283" data-file-height="319" /></a><figcaption><a href="/wiki/Aufbau_principle#Madelung_energy_ordering_rule" title="Aufbau principle">The Madelung energy ordering rule</a> describes the order in which orbitals are arranged by increasing energy according to the Madelung rule. Each diagonal corresponds to a different value of n + l.</figcaption></figure> <p>Modern <a href="/wiki/Quantum_mechanics" title="Quantum mechanics">quantum mechanics</a> explains these <a href="/wiki/Periodic_trends" title="Periodic trends">periodic trends</a> in properties in terms of <a href="/wiki/Electron_shell" title="Electron shell">electron shells</a>. As atomic number increases, shells fill with electrons in approximately the order shown in the ordering rule diagram. The filling of each shell corresponds to a row in the table. </p><p>In the <a href="/wiki/F-block" class="mw-redirect" title="F-block">f-block</a> and <a href="/wiki/P-block" class="mw-redirect" title="P-block">p-block</a> of the periodic table, elements within the same period generally do not exhibit trends and similarities in properties (vertical trends down groups are more significant). However, in the <a href="/wiki/D-block" class="mw-redirect" title="D-block">d-block</a>, trends across periods become significant, and in the <a href="/wiki/F-block" class="mw-redirect" title="F-block">f-block</a> elements show a high degree of similarity across periods. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Periods">Periods</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_(periodic_table)&action=edit&section=1" title="Edit section: Periods"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>There are currently seven complete periods in the periodic table, comprising the 118 known elements. Any new elements will be placed into an eighth period; see <a href="/wiki/Extended_periodic_table" title="Extended periodic table">extended periodic table</a>. The elements are colour-coded below by their <a href="/wiki/Block_(periodic_table)" title="Block (periodic table)">block</a>: red for the s-block, yellow for the p-block, blue for the d-block, and green for the f-block. </p> <div class="mw-heading mw-heading3"><h3 id="Period_1">Period 1</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_(periodic_table)&action=edit&section=2" title="Edit section: Period 1"><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/Period_1_element" title="Period 1 element">Period 1 element</a></div> <table style="text-align:center;"> <tbody><tr> <th><a href="/wiki/Periodic_table_group" class="mw-redirect" title="Periodic table group">Group</a> </th> <th><a href="/wiki/Alkali_metal" title="Alkali metal">1</a> </th> <th><a href="/wiki/Noble_gas" title="Noble gas">18</a> </th></tr> <tr> <th><small>Atomic #</small><br />Name </th> <td bgcolor="#ff9999"><span style="color:green;">1</span><br /><a href="/wiki/Hydrogen" title="Hydrogen">H</a> </td> <td bgcolor="#ff9999"><span style="color:green;">2</span><br /><a href="/wiki/Helium" title="Helium">He</a> </td></tr></tbody></table> <p>The first period contains fewer elements than any other, with only two, <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a> and <a href="/wiki/Helium" title="Helium">helium</a>. They therefore do not follow the <a href="/wiki/Octet_rule" title="Octet rule">octet rule</a>, but rather a <a href="/wiki/Duplet_rule" class="mw-redirect" title="Duplet rule">duplet rule</a>. Chemically, helium behaves like a <a href="/wiki/Noble_gas" title="Noble gas">noble gas</a>, and thus is taken to be part of the <a href="/wiki/Group_18_element" class="mw-redirect" title="Group 18 element">group 18 elements</a>. However, in terms of its nuclear structure it belongs to the <a href="/wiki/S-block" class="mw-redirect" title="S-block">s-block</a>, and is therefore sometimes classified as a <a href="/wiki/Group_2_element" class="mw-redirect" title="Group 2 element">group 2 element</a>, or simultaneously both 2 and 18. Hydrogen readily loses and gains an electron, and so behaves chemically as both a <a href="/wiki/Group_1_element" class="mw-redirect" title="Group 1 element">group 1</a> and a <a href="/wiki/Group_17_element" class="mw-redirect" title="Group 17 element">group 17 element</a>. </p> <ul><li><a href="/wiki/Hydrogen" title="Hydrogen">Hydrogen</a> (H) 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-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Ionized hydrogen is just a <a href="/wiki/Proton" title="Proton">proton</a>. <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 <a href="/wiki/Methane" title="Methane">methane</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-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Helium" title="Helium">Helium</a> (He) exists only as a <a href="/wiki/Gas" title="Gas">gas</a> except in extreme conditions.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> It is the second-lightest element and is the second-most abundant in the universe.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<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 created through <a href="/wiki/Nuclear_fusion" title="Nuclear fusion">nuclear fusion</a> of hydrogen in stars.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> On <a href="/wiki/Earth" title="Earth">Earth</a>, helium is relatively rare, only occurring as a byproduct of the natural <a href="/wiki/Radioactive_decay" title="Radioactive decay">decay</a> of some radioactive elements.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Such 'radiogenic' helium is trapped within <a href="/wiki/Natural_gas" title="Natural gas">natural gas</a> in concentrations of up to seven percent by volume.<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></li></ul> <div class="mw-heading mw-heading3"><h3 id="Period_2">Period 2</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_(periodic_table)&action=edit&section=3" title="Edit section: Period 2"><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/Period_2_element" title="Period 2 element">Period 2 element</a></div> <table style="text-align:center;"> <tbody><tr> <th><a href="/wiki/Periodic_table_group" class="mw-redirect" title="Periodic table group">Group</a> </th> <th><a href="/wiki/Alkali_metal" title="Alkali metal">1</a> </th> <th><a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal">2</a> </th> <th><a href="/wiki/Boron_group" title="Boron group">13</a> </th> <th><a href="/wiki/Carbon_group" title="Carbon group">14</a> </th> <th><a href="/wiki/Pnictogen" title="Pnictogen">15</a> </th> <th><a href="/wiki/Chalcogen" title="Chalcogen">16</a> </th> <th><a href="/wiki/Halogen" title="Halogen">17</a> </th> <th><a href="/wiki/Noble_gas" title="Noble gas">18</a> </th></tr> <tr> <th><small>Atomic #</small><br />Name </th> <td bgcolor="#ff9999">3<br /><a href="/wiki/Lithium" title="Lithium">Li</a> </td> <td bgcolor="#ff9999">4<br /><a href="/wiki/Beryllium" title="Beryllium">Be</a> </td> <td bgcolor="#fdff8c">5<br /><a href="/wiki/Boron" title="Boron">B</a> </td> <td bgcolor="#fdff8c">6<br /><a href="/wiki/Carbon" title="Carbon">C</a> </td> <td bgcolor="#fdff8c"><span style="color:green;">7</span><br /><a href="/wiki/Nitrogen" title="Nitrogen">N</a> </td> <td bgcolor="#fdff8c"><span style="color:green;">8</span><br /><a href="/wiki/Oxygen" title="Oxygen">O</a> </td> <td bgcolor="#fdff8c"><span style="color:green;">9</span><br /><a href="/wiki/Fluorine" title="Fluorine">F</a> </td> <td bgcolor="#fdff8c"><span style="color:green;">10</span><br /><a href="/wiki/Neon" title="Neon">Ne</a> </td></tr></tbody></table> <p>Period 2 elements involve the <a href="/wiki/S-block" class="mw-redirect" title="S-block">2s</a> and <a href="/wiki/P-block" class="mw-redirect" title="P-block">2p</a> <a href="/wiki/Atomic_orbital" title="Atomic orbital">orbitals</a>. They include the biologically most essential elements besides hydrogen: carbon, nitrogen, and oxygen. </p> <ul><li><a href="/wiki/Lithium" title="Lithium">Lithium</a> (Li) is the lightest metal and the least dense solid element.<sup id="cite_ref-weli_8-0" class="reference"><a href="#cite_note-weli-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> In its non-ionized state it is one of the most reactive elements, and so is only ever found naturally in <a href="/wiki/Chemical_compound" title="Chemical compound">compounds</a>. It is the heaviest <a href="/wiki/Primordial_element" class="mw-redirect" title="Primordial element">primordial element</a> forged in large quantities during the <a href="/wiki/Big_Bang" title="Big Bang">Big Bang</a>.</li> <li><a href="/wiki/Beryllium" title="Beryllium">Beryllium</a> (Be) has one of the highest <a href="/wiki/Melting_point" title="Melting point">melting points</a> of all the <a href="/wiki/Light_metal" title="Light metal">light metals</a>. Small amounts of beryllium were <a href="/wiki/Big_Bang_nucleosynthesis" title="Big Bang nucleosynthesis">synthesised</a> during the Big Bang, although most of it <a href="/wiki/Nuclear_decay" class="mw-redirect" title="Nuclear decay">decayed</a> or reacted further within stars to create larger nuclei, like carbon, nitrogen or oxygen. Beryllium is classified by the <a href="/wiki/International_Agency_for_Research_on_Cancer" title="International Agency for Research on Cancer">International Agency for Research on Cancer</a> as a <a href="/wiki/List_of_IARC_Group_1_carcinogens" class="mw-redirect" title="List of IARC Group 1 carcinogens">group 1 carcinogen</a>.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Between 1% and 15% of people are sensitive to beryllium and may develop an inflammatory reaction in their <a href="/wiki/Respiratory_system" title="Respiratory system">respiratory system</a> and <a href="/wiki/Skin" title="Skin">skin</a>, called chronic beryllium disease.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Boron" title="Boron">Boron</a> (B) does not occur naturally as a free element, but in compounds such as <a href="/wiki/Borate" title="Borate">borates</a>. It is an essential plant <a href="/wiki/Micronutrient" title="Micronutrient">micronutrient</a>, required for cell wall strength and development, cell division, seed and fruit development, sugar transport and hormone development,<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><sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> though high levels are toxic.</li> <li><a href="/wiki/Carbon" title="Carbon">Carbon</a> (C) is the fourth-most abundant element in the universe by mass after <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a>, <a href="/wiki/Helium" title="Helium">helium</a> and oxygen<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> and is the <a href="/wiki/Composition_of_the_human_body" title="Composition of the human body">second-most abundant element in the human body</a> by mass after oxygen,<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> the third-most abundant by number of atoms.<sup id="cite_ref-Freitas_15-0" class="reference"><a href="#cite_note-Freitas-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> There are an almost infinite number of compounds that contain carbon due to carbon's ability to form long stable chains of C—C bonds.<sup id="cite_ref-hydrocarbon_16-0" class="reference"><a href="#cite_note-hydrocarbon-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-acell_17-0" class="reference"><a href="#cite_note-acell-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> All <a href="/wiki/Organic_compound" title="Organic compound">organic compounds</a>, those essential for life, contain at least one atom of carbon;<sup id="cite_ref-hydrocarbon_16-1" class="reference"><a href="#cite_note-hydrocarbon-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-acell_17-1" class="reference"><a href="#cite_note-acell-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> combined with hydrogen, oxygen, nitrogen, sulfur, and phosphorus, carbon is the basis of every important biological compound.<sup id="cite_ref-acell_17-2" class="reference"><a href="#cite_note-acell-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Nitrogen" title="Nitrogen">Nitrogen</a> (N) is found mainly as mostly <a href="/wiki/Inert_gas" title="Inert gas">inert</a> <a href="/wiki/Diatomic" class="mw-redirect" title="Diatomic">diatomic</a> gas, N<sub>2</sub>, which makes up 78% of the Earth's atmosphere by volume. It is an essential component of <a href="/wiki/Protein" title="Protein">proteins</a> and therefore of life.</li> <li><a href="/wiki/Oxygen" title="Oxygen">Oxygen</a> (O) comprising 21% of the atmosphere by volume and is required for <a href="/wiki/Respiration_(physiology)" title="Respiration (physiology)">respiration</a> by all (or nearly all) animals, as well as being the principal component of <a href="/wiki/Water" title="Water">water</a>. Oxygen is the third-most abundant element in the universe, and oxygen compounds dominate the Earth's crust.</li> <li><a href="/wiki/Fluorine" title="Fluorine">Fluorine</a> (F) is the most reactive element in its non-ionized state, and so is never found that way in nature.</li> <li><a href="/wiki/Neon" title="Neon">Neon</a> (Ne) is a <a href="/wiki/Noble_gas" title="Noble gas">noble gas</a> used in <a href="/wiki/Neon_lighting" title="Neon lighting">neon lighting</a>.</li></ul> <div class="mw-heading mw-heading3"><h3 id="Period_3">Period 3</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_(periodic_table)&action=edit&section=4" title="Edit section: Period 3"><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/Period_3_element" title="Period 3 element">Period 3 element</a></div> <table style="text-align:center;"> <tbody><tr> <th><a href="/wiki/Periodic_table_group" class="mw-redirect" title="Periodic table group">Group</a> </th> <th><a href="/wiki/Alkali_metal" title="Alkali metal">1</a> </th> <th><a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal">2</a> </th> <th><a href="/wiki/Boron_group" title="Boron group">13</a> </th> <th><a href="/wiki/Carbon_group" title="Carbon group">14</a> </th> <th><a href="/wiki/Pnictogen" title="Pnictogen">15</a> </th> <th><a href="/wiki/Chalcogen" title="Chalcogen">16</a> </th> <th><a href="/wiki/Halogen" title="Halogen">17</a> </th> <th><a href="/wiki/Noble_gas" title="Noble gas">18</a> </th></tr> <tr> <th><small>Atomic #</small><br />Name </th> <td bgcolor="#ff9999">11<br /><a href="/wiki/Sodium" title="Sodium">Na</a> </td> <td bgcolor="#ff9999">12<br /><a href="/wiki/Magnesium" title="Magnesium">Mg</a> </td> <td bgcolor="#fdff8c">13<br /><a href="/wiki/Aluminium" title="Aluminium">Al</a> </td> <td bgcolor="#fdff8c">14<br /><a href="/wiki/Silicon" title="Silicon">Si</a> </td> <td bgcolor="#fdff8c">15<br /><a href="/wiki/Phosphorus" title="Phosphorus">P</a> </td> <td bgcolor="#fdff8c">16<br /><a href="/wiki/Sulfur" title="Sulfur">S</a> </td> <td bgcolor="#fdff8c"><span style="color:green;">17</span><br /><a href="/wiki/Chlorine" title="Chlorine">Cl</a> </td> <td bgcolor="#fdff8c"><span style="color:green;">18</span><br /><a href="/wiki/Argon" title="Argon">Ar</a> </td></tr></tbody></table> <p>All period three elements occur in nature and have at least one <a href="/wiki/Stable_nuclide" title="Stable nuclide">stable isotope</a>. All but the noble gas <a href="/wiki/Argon" title="Argon">argon</a> are essential to basic geology and biology. </p> <ul><li><a href="/wiki/Sodium" title="Sodium">Sodium</a> (Na) is an <a href="/wiki/Alkali_metal" title="Alkali metal">alkali metal</a>. It is present in Earth's oceans in large quantities in the form of <a href="/wiki/Sodium_chloride" title="Sodium chloride">sodium chloride</a> (table salt).</li> <li><a href="/wiki/Magnesium" title="Magnesium">Magnesium</a> (Mg) is an <a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal">alkaline earth metal</a>. Magnesium <a href="/wiki/Ion" title="Ion">ions</a> are found in <a href="/wiki/Chlorophyll" title="Chlorophyll">chlorophyll</a>.</li> <li><a href="/wiki/Aluminium" title="Aluminium">Aluminium</a> (Al) is a <a href="/wiki/Post-transition_metal" title="Post-transition metal">post-transition metal</a>. It is the most abundant metal in the Earth's <a href="/wiki/Crust_(geology)" title="Crust (geology)">crust</a>.</li> <li><a href="/wiki/Silicon" title="Silicon">Silicon</a> (Si) is a <a href="/wiki/Metalloid" title="Metalloid">metalloid</a>. It is a <a href="/wiki/Semiconductor" title="Semiconductor">semiconductor</a>, making it the principal component in many <a href="/wiki/Integrated_circuits" class="mw-redirect" title="Integrated circuits">integrated circuits</a>. <a href="/wiki/Silicon_dioxide" title="Silicon dioxide">Silicon dioxide</a> is the principal constituent of <a href="/wiki/Sand" title="Sand">sand</a>. As Carbon is to <a href="/wiki/Biology" title="Biology">Biology</a>, Silicon is to <a href="/wiki/Geology" title="Geology">Geology</a>.</li> <li><a href="/wiki/Phosphorus" title="Phosphorus">Phosphorus</a> (P) is a <a href="/wiki/Nonmetal_(chemistry)" class="mw-redirect" title="Nonmetal (chemistry)">nonmetal</a> essential to <a href="/wiki/DNA" title="DNA">DNA</a>. It is highly <a href="/wiki/Reactivity_(chemistry)" title="Reactivity (chemistry)">reactive</a>, and as such is never found in nature as a free element.</li> <li><a href="/wiki/Sulfur" title="Sulfur">Sulfur</a> (S) is a <a href="/wiki/Nonmetal_(chemistry)" class="mw-redirect" title="Nonmetal (chemistry)">nonmetal</a>. It is found in two <a href="/wiki/Amino_acid" title="Amino acid">amino acids</a>: <a href="/wiki/Cysteine" title="Cysteine">cysteine</a> and <a href="/wiki/Methionine" title="Methionine">methionine</a>.</li> <li><a href="/wiki/Chlorine" title="Chlorine">Chlorine</a> (Cl) is a <a href="/wiki/Halogen" title="Halogen">halogen</a>. Since it is one of the most reactive elements, it is often found on the Earth's surface as sodium chloride. Its compounds used as a disinfectant, especially in <a href="/wiki/Swimming_pool" title="Swimming pool">swimming pools</a>.</li> <li><a href="/wiki/Argon" title="Argon">Argon</a> (Ar) is a <a href="/wiki/Noble_gas" title="Noble gas">noble gas</a>, making it almost entirely nonreactive. <a href="/wiki/Incandescent_lamp" class="mw-redirect" title="Incandescent lamp">Incandescent lamps</a> are often filled with noble gases such as argon in order to preserve the filaments at high temperatures.</li></ul> <div class="mw-heading mw-heading3"><h3 id="Period_4">Period 4</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_(periodic_table)&action=edit&section=5" title="Edit section: Period 4"><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/Period_4_element" title="Period 4 element">Period 4 element</a></div> <table style="text-align:center;"> <tbody><tr> <th><a href="/wiki/Periodic_table_group" class="mw-redirect" title="Periodic table group">Group</a> </th> <th><a href="/wiki/Alkali_metal" title="Alkali metal">1</a> </th> <th><a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal">2</a> </th> <th><a href="/wiki/Group_3_element" title="Group 3 element">3</a> </th> <th><a href="/wiki/Group_4_element" title="Group 4 element">4</a> </th> <th><a href="/wiki/Group_5_element" title="Group 5 element">5</a> </th> <th><a href="/wiki/Group_6_element" title="Group 6 element">6</a> </th> <th><a href="/wiki/Group_7_element" title="Group 7 element">7</a> </th> <th><a href="/wiki/Group_8_element" title="Group 8 element">8</a> </th> <th><a href="/wiki/Group_9_element" title="Group 9 element">9</a> </th> <th><a href="/wiki/Group_10_element" title="Group 10 element">10</a> </th> <th><a href="/wiki/Group_11_element" title="Group 11 element">11</a> </th> <th><a href="/wiki/Group_12_element" title="Group 12 element">12</a> </th> <th><a href="/wiki/Boron_group" title="Boron group">13</a> </th> <th><a href="/wiki/Carbon_group" title="Carbon group">14</a> </th> <th><a href="/wiki/Pnictogen" title="Pnictogen">15</a> </th> <th><a href="/wiki/Chalcogen" title="Chalcogen">16</a> </th> <th><a href="/wiki/Halogen" title="Halogen">17</a> </th> <th><a href="/wiki/Noble_gas" title="Noble gas">18</a> </th></tr> <tr> <th><small>Atomic #</small><br />Name </th> <td bgcolor="#ff9999">19<br /><a href="/wiki/Potassium" title="Potassium">K</a> </td> <td bgcolor="#ff9999">20<br /><a href="/wiki/Calcium" title="Calcium">Ca</a> </td> <td bgcolor="#99ccff">21<br /><a href="/wiki/Scandium" title="Scandium">Sc</a> </td> <td bgcolor="#99ccff">22<br /><a href="/wiki/Titanium" title="Titanium">Ti</a> </td> <td bgcolor="#99ccff">23<br /><a href="/wiki/Vanadium" title="Vanadium">V</a> </td> <td bgcolor="#99ccff">24<br /><a href="/wiki/Chromium" title="Chromium">Cr</a> </td> <td bgcolor="#99ccff">25<br /><a href="/wiki/Manganese" title="Manganese">Mn</a> </td> <td bgcolor="#99ccff">26<br /><a href="/wiki/Iron" title="Iron">Fe</a> </td> <td bgcolor="#99ccff">27<br /><a href="/wiki/Cobalt" title="Cobalt">Co</a> </td> <td bgcolor="#99ccff">28<br /><a href="/wiki/Nickel" title="Nickel">Ni</a> </td> <td bgcolor="#99ccff">29<br /><a href="/wiki/Copper" title="Copper">Cu</a> </td> <td bgcolor="#99ccff">30<br /><a href="/wiki/Zinc" title="Zinc">Zn</a> </td> <td bgcolor="#fdff8c">31<br /><a href="/wiki/Gallium" title="Gallium">Ga</a> </td> <td bgcolor="#fdff8c">32<br /><a href="/wiki/Germanium" title="Germanium">Ge</a> </td> <td bgcolor="#fdff8c">33<br /><a href="/wiki/Arsenic" title="Arsenic">As</a> </td> <td bgcolor="#fdff8c">34<br /><a href="/wiki/Selenium" title="Selenium">Se</a> </td> <td bgcolor="#fdff8c"><span style="color:blue;">35</span><br /><a href="/wiki/Bromine" title="Bromine">Br</a> </td> <td bgcolor="#fdff8c"><span style="color:green;">36</span><br /><a href="/wiki/Krypton" title="Krypton">Kr</a> </td></tr></tbody></table> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Coloured-transition-metal-solutions.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/57/Coloured-transition-metal-solutions.jpg/400px-Coloured-transition-metal-solutions.jpg" decoding="async" width="400" height="147" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/57/Coloured-transition-metal-solutions.jpg/600px-Coloured-transition-metal-solutions.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/57/Coloured-transition-metal-solutions.jpg/800px-Coloured-transition-metal-solutions.jpg 2x" data-file-width="1100" data-file-height="404" /></a><figcaption>From left to right, aqueous solutions of: <a href="/wiki/Cobalt(II)_nitrate" title="Cobalt(II) nitrate">Co(NO<sub>3</sub>)<sub>2</sub></a> (red); <a href="/wiki/Potassium_dichromate" title="Potassium dichromate">K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub></a> (orange); <a href="/wiki/Potassium_chromate" title="Potassium chromate">K<sub>2</sub>CrO<sub>4</sub></a> (yellow); <a href="/wiki/Nickel(II)_chloride" title="Nickel(II) chloride">NiCl<sub>2</sub></a> (green); <a href="/wiki/Copper(II)_sulfate" title="Copper(II) sulfate">CuSO<sub>4</sub></a> (blue); <a href="/wiki/Potassium_permanganate" title="Potassium permanganate">KMnO<sub>4</sub></a> (purple).</figcaption></figure> <p>Period 4 includes the biologically essential elements <a href="/wiki/Potassium" title="Potassium">potassium</a> and <a href="/wiki/Calcium" title="Calcium">calcium</a>, and is the first period in the <a href="/wiki/D-block" class="mw-redirect" title="D-block">d-block</a> with the lighter <a href="/wiki/Transition_metals" class="mw-redirect" title="Transition metals">transition metals</a>. These include <a href="/wiki/Iron" title="Iron">iron</a>, the heaviest element forged in <a href="/wiki/Main-sequence_star" class="mw-redirect" title="Main-sequence star">main-sequence stars</a> and a principal component of the Earth, as well as other important metals such as <a href="/wiki/Cobalt" title="Cobalt">cobalt</a>, <a href="/wiki/Nickel" title="Nickel">nickel</a>, and <a href="/wiki/Copper" title="Copper">copper</a>. Almost all have biological roles. </p><p>Completing the fourth period are six p-block elements: <a href="/wiki/Gallium" title="Gallium">gallium</a>, <a href="/wiki/Germanium" title="Germanium">germanium</a>, <a href="/wiki/Arsenic" title="Arsenic">arsenic</a>, <a href="/wiki/Selenium" title="Selenium">selenium</a>, <a href="/wiki/Bromine" title="Bromine">bromine</a>, and <a href="/wiki/Krypton" title="Krypton">krypton</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Period_5">Period 5</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_(periodic_table)&action=edit&section=6" title="Edit section: Period 5"><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/Period_5_element" title="Period 5 element">Period 5 element</a></div> <table style="text-align:center;"> <tbody><tr> <th><a href="/wiki/Periodic_table_group" class="mw-redirect" title="Periodic table group">Group</a> </th> <th><a href="/wiki/Alkali_metal" title="Alkali metal">1</a> </th> <th><a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal">2</a> </th> <th><a href="/wiki/Group_3_element" title="Group 3 element">3</a> </th> <th><a href="/wiki/Group_4_element" title="Group 4 element">4</a> </th> <th><a href="/wiki/Group_5_element" title="Group 5 element">5</a> </th> <th><a href="/wiki/Group_6_element" title="Group 6 element">6</a> </th> <th><a href="/wiki/Group_7_element" title="Group 7 element">7</a> </th> <th><a href="/wiki/Group_8_element" title="Group 8 element">8</a> </th> <th><a href="/wiki/Group_9_element" title="Group 9 element">9</a> </th> <th><a href="/wiki/Group_10_element" title="Group 10 element">10</a> </th> <th><a href="/wiki/Group_11_element" title="Group 11 element">11</a> </th> <th><a href="/wiki/Group_12_element" title="Group 12 element">12</a> </th> <th><a href="/wiki/Boron_group" title="Boron group">13</a> </th> <th><a href="/wiki/Carbon_group" title="Carbon group">14</a> </th> <th><a href="/wiki/Pnictogen" title="Pnictogen">15</a> </th> <th><a href="/wiki/Chalcogen" title="Chalcogen">16</a> </th> <th><a href="/wiki/Halogen" title="Halogen">17</a> </th> <th><a href="/wiki/Noble_gas" title="Noble gas">18</a> </th></tr> <tr> <th><small>Atomic #</small><br />Name </th> <td bgcolor="#ff9999">37<br /><a href="/wiki/Rubidium" title="Rubidium">Rb</a> </td> <td bgcolor="#ff9999">38<br /><a href="/wiki/Strontium" title="Strontium">Sr</a> </td> <td bgcolor="#99ccff">39<br /><a href="/wiki/Yttrium" title="Yttrium">Y</a> </td> <td bgcolor="#99ccff">40<br /><a href="/wiki/Zirconium" title="Zirconium">Zr</a> </td> <td bgcolor="#99ccff">41<br /><a href="/wiki/Niobium" title="Niobium">Nb</a> </td> <td bgcolor="#99ccff">42<br /><a href="/wiki/Molybdenum" title="Molybdenum">Mo</a> </td> <td bgcolor="#99ccff">43<br /><a href="/wiki/Technetium" title="Technetium">Tc</a> </td> <td bgcolor="#99ccff">44<br /><a href="/wiki/Ruthenium" title="Ruthenium">Ru</a> </td> <td bgcolor="#99ccff">45<br /><a href="/wiki/Rhodium" title="Rhodium">Rh</a> </td> <td bgcolor="#99ccff">46<br /><a href="/wiki/Palladium" title="Palladium">Pd</a> </td> <td bgcolor="#99ccff">47<br /><a href="/wiki/Silver" title="Silver">Ag</a> </td> <td bgcolor="#99ccff">48<br /><a href="/wiki/Cadmium" title="Cadmium">Cd</a> </td> <td bgcolor="#fdff8c">49<br /><a href="/wiki/Indium" title="Indium">In</a> </td> <td bgcolor="#fdff8c">50<br /><a href="/wiki/Tin" title="Tin">Sn</a> </td> <td bgcolor="#fdff8c">51<br /><a href="/wiki/Antimony" title="Antimony">Sb</a> </td> <td bgcolor="#fdff8c">52<br /><a href="/wiki/Tellurium" title="Tellurium">Te</a> </td> <td bgcolor="#fdff8c">53<br /><a href="/wiki/Iodine" title="Iodine">I</a> </td> <td bgcolor="#fdff8c"><span style="color:green;">54</span><br /><a href="/wiki/Xenon" title="Xenon">Xe</a> </td></tr></tbody></table> <p>Period 5 has the same number of elements as period 4 and follows the same general structure but with one more post transition metal and one fewer nonmetal. Of the three heaviest elements with biological roles, two (<a href="/wiki/Molybdenum" title="Molybdenum">molybdenum</a> and <a href="/wiki/Iodine" title="Iodine">iodine</a>) are in this period; <a href="/wiki/Tungsten" title="Tungsten">tungsten</a>, in period 6, is heavier, along with several of the early <a href="/wiki/Lanthanide" title="Lanthanide">lanthanides</a>. Period 5 also includes <a href="/wiki/Technetium" title="Technetium">technetium</a>, the lightest exclusively <a href="/wiki/Radioactive_decay" title="Radioactive decay">radioactive</a> element. </p> <div class="mw-heading mw-heading3"><h3 id="Period_6">Period 6</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_(periodic_table)&action=edit&section=7" title="Edit section: Period 6"><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/Period_6_element" title="Period 6 element">Period 6 element</a></div> <table style="text-align:center;"> <tbody><tr> <th><a href="/wiki/Periodic_table_group" class="mw-redirect" title="Periodic table group">Group</a> </th> <th><a href="/wiki/Alkali_metal" title="Alkali metal">1</a> </th> <th><a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal">2</a> </th> <th colspan="14" align="center">  </th> <th><a href="/wiki/Group_3_element" title="Group 3 element">3</a> </th> <th><a href="/wiki/Group_4_element" title="Group 4 element">4</a> </th> <th><a href="/wiki/Group_5_element" title="Group 5 element">5</a> </th> <th><a href="/wiki/Group_6_element" title="Group 6 element">6</a> </th> <th><a href="/wiki/Group_7_element" title="Group 7 element">7</a> </th> <th><a href="/wiki/Group_8_element" title="Group 8 element">8</a> </th> <th><a href="/wiki/Group_9_element" title="Group 9 element">9</a> </th> <th><a href="/wiki/Group_10_element" title="Group 10 element">10</a> </th> <th><a href="/wiki/Group_11_element" title="Group 11 element">11</a> </th> <th><a href="/wiki/Group_12_element" title="Group 12 element">12</a> </th> <th><a href="/wiki/Boron_group" title="Boron group">13</a> </th> <th><a href="/wiki/Carbon_group" title="Carbon group">14</a> </th> <th><a href="/wiki/Pnictogen" title="Pnictogen">15</a> </th> <th><a href="/wiki/Chalcogen" title="Chalcogen">16</a> </th> <th><a href="/wiki/Halogen" title="Halogen">17</a> </th> <th><a href="/wiki/Noble_gas" title="Noble gas">18</a> </th></tr> <tr> <th><small>Atomic #</small><br />Name </th> <td bgcolor="#ff9999">55<br /><a href="/wiki/Caesium" title="Caesium">Cs</a> </td> <td bgcolor="#ff9999">56<br /><a href="/wiki/Barium" title="Barium">Ba</a> </td> <td bgcolor="#9bff99">57<br /><a href="/wiki/Lanthanum" title="Lanthanum">La</a> </td> <td bgcolor="#9bff99">58<br /><a href="/wiki/Cerium" title="Cerium">Ce</a> </td> <td bgcolor="#9bff99">59<br /><a href="/wiki/Praseodymium" title="Praseodymium">Pr</a> </td> <td bgcolor="#9bff99">60<br /><a href="/wiki/Neodymium" title="Neodymium">Nd</a> </td> <td bgcolor="#9bff99">61<br /><a href="/wiki/Promethium" title="Promethium">Pm</a> </td> <td bgcolor="#9bff99">62<br /><a href="/wiki/Samarium" title="Samarium">Sm</a> </td> <td bgcolor="#9bff99">63<br /><a href="/wiki/Europium" title="Europium">Eu</a> </td> <td bgcolor="#9bff99">64<br /><a href="/wiki/Gadolinium" title="Gadolinium">Gd</a> </td> <td bgcolor="#9bff99">65<br /><a href="/wiki/Terbium" title="Terbium">Tb</a> </td> <td bgcolor="#9bff99">66<br /><a href="/wiki/Dysprosium" title="Dysprosium">Dy</a> </td> <td bgcolor="#9bff99">67<br /><a href="/wiki/Holmium" title="Holmium">Ho</a> </td> <td bgcolor="#9bff99">68<br /><a href="/wiki/Erbium" title="Erbium">Er</a> </td> <td bgcolor="#9bff99">69<br /><a href="/wiki/Thulium" title="Thulium">Tm</a> </td> <td bgcolor="#9bff99">70<br /><a href="/wiki/Ytterbium" title="Ytterbium">Yb</a> </td> <td bgcolor="#99ccff">71<br /><a href="/wiki/Lutetium" title="Lutetium">Lu</a> </td> <td bgcolor="#99ccff">72<br /><a href="/wiki/Hafnium" title="Hafnium">Hf</a> </td> <td bgcolor="#99ccff">73<br /><a href="/wiki/Tantalum" title="Tantalum">Ta</a> </td> <td bgcolor="#99ccff">74<br /><a href="/wiki/Tungsten" title="Tungsten">W</a> </td> <td bgcolor="#99ccff">75<br /><a href="/wiki/Rhenium" title="Rhenium">Re</a> </td> <td bgcolor="#99ccff">76<br /><a href="/wiki/Osmium" title="Osmium">Os</a> </td> <td bgcolor="#99ccff">77<br /><a href="/wiki/Iridium" title="Iridium">Ir</a> </td> <td bgcolor="#99ccff">78<br /><a href="/wiki/Platinum" title="Platinum">Pt</a> </td> <td bgcolor="#99ccff">79<br /><a href="/wiki/Gold" title="Gold">Au</a> </td> <td bgcolor="#99ccff"><span style="color:blue;">80</span><br /><a href="/wiki/Mercury_(element)" title="Mercury (element)">Hg</a> </td> <td bgcolor="#fdff8c">81<br /><a href="/wiki/Thallium" title="Thallium">Tl</a> </td> <td bgcolor="#fdff8c">82<br /><a href="/wiki/Lead" title="Lead">Pb</a> </td> <td bgcolor="#fdff8c">83<br /><a href="/wiki/Bismuth" title="Bismuth">Bi</a> </td> <td bgcolor="#fdff8c">84<br /><a href="/wiki/Polonium" title="Polonium">Po</a> </td> <td bgcolor="#fdff8c">85<br /><a href="/wiki/Astatine" title="Astatine">At</a> </td> <td bgcolor="#fdff8c"><span style="color:green;">86</span><br /><a href="/wiki/Radon" title="Radon">Rn</a> </td></tr></tbody></table> <p>Period 6 is the first period to include the <a href="/wiki/F-block" class="mw-redirect" title="F-block">f-block</a>, with the <a href="/wiki/Lanthanide" title="Lanthanide">lanthanides</a> (also known as the <a href="/wiki/Rare_earth_element" class="mw-redirect" title="Rare earth element">rare earth elements</a>), and includes the heaviest stable elements. Many of these <a href="/wiki/Heavy_metals" class="mw-redirect" title="Heavy metals">heavy metals</a> are toxic and some are radioactive, but <a href="/wiki/Platinum" title="Platinum">platinum</a> and <a href="/wiki/Gold" title="Gold">gold</a> are largely inert. </p> <div class="mw-heading mw-heading3"><h3 id="Period_7">Period 7</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_(periodic_table)&action=edit&section=8" title="Edit section: Period 7"><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/Period_7_element" title="Period 7 element">Period 7 element</a></div> <table style="text-align:center;"> <tbody><tr> <th><a href="/wiki/Periodic_table_group" class="mw-redirect" title="Periodic table group">Group</a> </th> <th><a href="/wiki/Alkali_metal" title="Alkali metal">1</a> </th> <th><a href="/wiki/Alkaline_earth_metal" title="Alkaline earth metal">2</a> </th> <th colspan="14" align="center">  </th> <th><a href="/wiki/Group_3_element" title="Group 3 element">3</a> </th> <th><a href="/wiki/Group_4_element" title="Group 4 element">4</a> </th> <th><a href="/wiki/Group_5_element" title="Group 5 element">5</a> </th> <th><a href="/wiki/Group_6_element" title="Group 6 element">6</a> </th> <th><a href="/wiki/Group_7_element" title="Group 7 element">7</a> </th> <th><a href="/wiki/Group_8_element" title="Group 8 element">8</a> </th> <th><a href="/wiki/Group_9_element" title="Group 9 element">9</a> </th> <th><a href="/wiki/Group_10_element" title="Group 10 element">10</a> </th> <th><a href="/wiki/Group_11_element" title="Group 11 element">11</a> </th> <th><a href="/wiki/Group_12_element" title="Group 12 element">12</a> </th> <th><a href="/wiki/Boron_group" title="Boron group">13</a> </th> <th><a href="/wiki/Carbon_group" title="Carbon group">14</a> </th> <th><a href="/wiki/Pnictogen" title="Pnictogen">15</a> </th> <th><a href="/wiki/Chalcogen" title="Chalcogen">16</a> </th> <th><a href="/wiki/Halogen" title="Halogen">17</a> </th> <th><a href="/wiki/Noble_gas" title="Noble gas">18</a> </th></tr> <tr> <th><small>Atomic #</small><br />Name </th> <td bgcolor="#ff9999">87<br /> <a href="/wiki/Francium" title="Francium">Fr</a>  </td> <td bgcolor="#ff9999">88<br /><a href="/wiki/Radium" title="Radium">Ra</a> </td> <td bgcolor="#9bff99">89<br /><a href="/wiki/Actinium" title="Actinium">Ac</a> </td> <td bgcolor="#9bff99">90<br /><a href="/wiki/Thorium" title="Thorium">Th</a> </td> <td bgcolor="#9bff99">91<br /><a href="/wiki/Protactinium" title="Protactinium">Pa</a> </td> <td bgcolor="#9bff99">92<br /><a href="/wiki/Uranium" title="Uranium">U</a> </td> <td bgcolor="#9bff99">93<br /><a href="/wiki/Neptunium" title="Neptunium">Np</a> </td> <td bgcolor="#9bff99">94<br /><a href="/wiki/Plutonium" title="Plutonium">Pu</a> </td> <td bgcolor="#9bff99">95<br /><a href="/wiki/Americium" title="Americium">Am</a> </td> <td bgcolor="#9bff99">96<br /><a href="/wiki/Curium" title="Curium">Cm</a> </td> <td bgcolor="#9bff99">97<br /><a href="/wiki/Berkelium" title="Berkelium">Bk</a> </td> <td bgcolor="#9bff99">98<br /><a href="/wiki/Californium" title="Californium">Cf</a> </td> <td bgcolor="#9bff99">99<br /><a href="/wiki/Einsteinium" title="Einsteinium">Es</a> </td> <td bgcolor="#9bff99"><span style="font-size:66%;">100</span><br /><a href="/wiki/Fermium" title="Fermium">Fm</a> </td> <td bgcolor="#9bff99"><span style="font-size:66%;">101</span><br /><a href="/wiki/Mendelevium" title="Mendelevium">Md</a> </td> <td bgcolor="#9bff99"><span style="font-size:66%;">102</span><br /><a href="/wiki/Nobelium" title="Nobelium">No</a> </td> <td bgcolor="#99ccff"><span style="font-size:66%;">103</span><br /><a href="/wiki/Lawrencium" title="Lawrencium">Lr</a> </td> <td bgcolor="#99ccff"><span style="color:gray; font-size:66%;">104</span><br /><a href="/wiki/Rutherfordium" title="Rutherfordium">Rf</a> </td> <td bgcolor="#99ccff"><span style="color:gray; font-size:66%;">105</span><br /><a href="/wiki/Dubnium" title="Dubnium">Db</a> </td> <td bgcolor="#99ccff"><span style="color:gray; font-size:66%;">106</span><br /><a href="/wiki/Seaborgium" title="Seaborgium">Sg</a> </td> <td bgcolor="#99ccff"><span style="color:gray; font-size:66%;">107</span><br /><a href="/wiki/Bohrium" title="Bohrium">Bh</a> </td> <td bgcolor="#99ccff"><span style="color:gray; font-size:66%;">108</span><br /><a href="/wiki/Hassium" title="Hassium">Hs</a> </td> <td bgcolor="#99ccff"><span style="color:gray; font-size:66%;">109</span><br /><a href="/wiki/Meitnerium" title="Meitnerium">Mt</a> </td> <td bgcolor="#99ccff"><span style="color:gray; font-size:66%;">110</span><br /><a href="/wiki/Darmstadtium" title="Darmstadtium">Ds</a> </td> <td bgcolor="#99ccff"><span style="color:gray; font-size:66%;">111</span><br /><a href="/wiki/Roentgenium" title="Roentgenium">Rg</a> </td> <td bgcolor="#99ccff"><span style="color:gray; font-size:66%;">112</span><br /><a href="/wiki/Copernicium" title="Copernicium">Cn</a> </td> <td bgcolor="#fdff8c"><span style="color:gray; font-size:66%;">113</span><br /><a href="/wiki/Nihonium" title="Nihonium">Nh</a> </td> <td bgcolor="#fdff8c"><span style="color:gray; font-size:66%;">114</span><br /><a href="/wiki/Flerovium" title="Flerovium">Fl</a> </td> <td bgcolor="#fdff8c"><span style="color:gray; font-size:66%;">115</span><br /><a href="/wiki/Moscovium" title="Moscovium">Mc</a> </td> <td bgcolor="#fdff8c"><span style="color:gray; font-size:66%;">116</span><br /><a href="/wiki/Livermorium" title="Livermorium">Lv</a> </td> <td bgcolor="#fdff8c"><span style="color:gray; font-size:66%;">117</span><br /><a href="/wiki/Tennessine" title="Tennessine">Ts</a> </td> <td bgcolor="#fdff8c"><span style="color:gray; font-size:66%;">118</span><br /><a href="/wiki/Oganesson" title="Oganesson">Og</a> </td></tr></tbody></table> <p>All elements of period 7 are <a href="/wiki/Radioactive" class="mw-redirect" title="Radioactive">radioactive</a>. This period contains the heaviest element which occurs naturally on Earth, <a href="/wiki/Plutonium" title="Plutonium">plutonium</a>. All of the subsequent elements in the period have been synthesized artificially. Whilst five of these (from <a href="/wiki/Americium" title="Americium">americium</a> to <a href="/wiki/Einsteinium" title="Einsteinium">einsteinium</a>) are now available in macroscopic quantities, most are extremely rare, having only been prepared in microgram amounts or less. Some of the later elements have only ever been identified in laboratories in quantities of a few atoms at a time. </p><p>Although the rarity of many of these elements means that experimental results are not very extensive, periodic and group trends in behaviour appear to be less well defined for period 7 than for other periods. Whilst <a href="/wiki/Francium" title="Francium">francium</a> and <a href="/wiki/Radium" title="Radium">radium</a> do show typical properties of groups 1 and 2, respectively, the <a href="/wiki/Actinides" class="mw-redirect" title="Actinides">actinides</a> display a much greater variety of behaviour and oxidation states than the <a href="/wiki/Lanthanides" class="mw-redirect" title="Lanthanides">lanthanides</a>. These peculiarities of period 7 may be due to a variety of factors, including a large degree of <a href="/wiki/Spin%E2%80%93orbit_coupling" class="mw-redirect" title="Spin–orbit coupling">spin–orbit coupling</a> and relativistic effects, ultimately caused by the very high positive electrical charge from their massive <a href="/wiki/Atomic_nuclei" class="mw-redirect" title="Atomic nuclei">atomic nuclei</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Period_8">Period 8</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_(periodic_table)&action=edit&section=9" title="Edit section: Period 8"><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/Extended_periodic_table" title="Extended periodic table">Extended periodic table</a></div> <p>No element of the eighth period has yet been synthesized. A <a href="/wiki/G-block" class="mw-redirect" title="G-block">g-block</a> is predicted. It is not clear if all elements predicted for the eighth period are in fact physically possible. Therefore, there may not be a ninth period. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Period_(periodic_table)&action=edit&section=10" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Group_(periodic_table)" title="Group (periodic table)">Group (periodic table)</a></li></ul> <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_(periodic_table)&action=edit&section=11" 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="CITEREFPalmer1997" class="citation web cs1">Palmer, David (November 13, 1997). <a rel="nofollow" class="external text" href="https://imagine.gsfc.nasa.gov/docs/ask_astro/answers/971113i.html">"Hydrogen in the Universe"</a>. 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"Functions of Boron in Plant Nutrition". <i>Annual Review of Plant Physiology and Plant Molecular Biology</i>. <b>49</b>: 481–500. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1146%2Fannurev.arplant.49.1.481">10.1146/annurev.arplant.49.1.481</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/15012243">15012243</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Annual+Review+of+Plant+Physiology+and+Plant+Molecular+Biology&rft.atitle=Functions+of+Boron+in+Plant+Nutrition&rft.volume=49&rft.pages=481-500&rft.date=1998&rft_id=info%3Adoi%2F10.1146%2Fannurev.arplant.49.1.481&rft_id=info%3Apmid%2F15012243&rft.aulast=Blevins&rft.aufirst=Dale+G.&rft.au=Lukaszewski%2C+Krystyna+M.&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+%28periodic+table%29" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://plymouthlibrary.org/faqelements.htm">Ten most abundant elements in the universe, taken from <i>The Top 10 of Everything</i>, 2006, Russell Ash, page 10. Retrieved October 15, 2008.</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100210170504/http://plymouthlibrary.org/faqelements.htm">Archived</a> February 10, 2010, at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFChang2007" class="citation book cs1">Chang, Raymond (2007). <i>Chemistry, Ninth Edition</i>. McGraw-Hill. p. 52. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-07-110595-6" title="Special:BookSources/0-07-110595-6"><bdi>0-07-110595-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Chemistry%2C+Ninth+Edition&rft.pages=52&rft.pub=McGraw-Hill&rft.date=2007&rft.isbn=0-07-110595-6&rft.aulast=Chang&rft.aufirst=Raymond&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+%28periodic+table%29" class="Z3988"></span></span> </li> <li id="cite_note-Freitas-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-Freitas_15-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFreitas_Jr.1999" class="citation book cs1">Freitas Jr., Robert A. (1999). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180416233300/http://www.foresight.org/Nanomedicine/Ch03_1.html"><i>Nanomedicine</i></a>. Landes Bioscience. Tables 3-1 & 3-2. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1-57059-680-8" title="Special:BookSources/1-57059-680-8"><bdi>1-57059-680-8</bdi></a>. Archived from <a rel="nofollow" class="external text" href="http://www.foresight.org/Nanomedicine/Ch03_1.html">the original</a> on 2018-04-16<span class="reference-accessdate">. Retrieved <span class="nowrap">2010-04-18</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Nanomedicine&rft.pages=Tables+3-1+%26+3-2&rft.pub=Landes+Bioscience&rft.date=1999&rft.isbn=1-57059-680-8&rft.aulast=Freitas+Jr.&rft.aufirst=Robert+A.&rft_id=http%3A%2F%2Fwww.foresight.org%2FNanomedicine%2FCh03_1.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+%28periodic+table%29" class="Z3988"></span></span> </li> <li id="cite_note-hydrocarbon-16"><span class="mw-cite-backlink">^ <a href="#cite_ref-hydrocarbon_16-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-hydrocarbon_16-1"><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="http://chemed.chem.purdue.edu/genchem/topicreview/bp/1organic/organic.html">"Structure and Nomenclature of Hydrocarbons"</a>. Purdue University<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-03-23</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Structure+and+Nomenclature+of+Hydrocarbons&rft.pub=Purdue+University&rft_id=http%3A%2F%2Fchemed.chem.purdue.edu%2Fgenchem%2Ftopicreview%2Fbp%2F1organic%2Forganic.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+%28periodic+table%29" class="Z3988"></span></span> </li> <li id="cite_note-acell-17"><span class="mw-cite-backlink">^ <a href="#cite_ref-acell_17-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-acell_17-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-acell_17-2"><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="CITEREFAlbertsAlexander_JohnsonJulian_LewisMartin_Raff" class="citation book cs1">Alberts, Bruce; Alexander Johnson; Julian Lewis; Martin Raff; Keith Roberts; Peter Walter. <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=carbon&rid=mboc4.section.165"><i>Molecular Biology of the Cell</i></a>. Garland Science.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Molecular+Biology+of+the+Cell&rft.pub=Garland+Science&rft.aulast=Alberts&rft.aufirst=Bruce&rft.au=Alexander+Johnson&rft.au=Julian+Lewis&rft.au=Martin+Raff&rft.au=Keith+Roberts&rft.au=Peter+Walter&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fbooks%2Fbv.fcgi%3Fhighlight%3Dcarbon%26rid%3Dmboc4.section.165&rfr_id=info%3Asid%2Fen.wikipedia.org%3APeriod+%28periodic+table%29" class="Z3988"></span></span> </li> </ol></div></div> <div class="navbox-styles"><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 .hlist.inline ol,.mw-parser-output .hlist.inline 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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 class="mw-selflink selflink">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 href="/wiki/Period_1_element" title="Period 1 element">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> <ul><li><b><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:Periodic_table" title="Category:Periodic table">Category</a></b></li> <li><b><span class="noviewer" typeof="mw:File"><span title="WikiProject"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/3/37/People_icon.svg/16px-People_icon.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/37/People_icon.svg/24px-People_icon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/37/People_icon.svg/32px-People_icon.svg.png 2x" data-file-width="100" data-file-height="100" /></span></span> <a href="/wiki/Wikipedia:WikiProject_Elements" title="Wikipedia:WikiProject Elements">WikiProject</a></b></li></ul> </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 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 href="/wiki/Period_1_element" title="Period 1 element">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 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