Unsur periode 1: Perbedaan antara revisi

[[Hidrogen]] kadang-kadang diletakkan di atas [[litium]],<ref name="iupac" /> di atas [[karbon]],<ref name="hydrogen">{{cite journal |last = Cronyn|first = Marshall W.|title = The Proper Place for Hydrogen in the Periodic Table|url = https://archive.org/details/sim_journal-of-chemical-education_2003-08_80_8/page/947|journal = Journal of Chemical Education|volume = 80|issue = 8|date = August 2003|pages = 947–951|doi = 10.1021/ed080p947|bibcode = 2003JChEd..80..947C}}</ref> di atas [[fluor]],<ref name="hydrogen" /><ref name="hydrogen-halogen">{{cite web|url = http://hydrogentwo.com/hydrogen-halogen.html|title = Hydrogen is a Halogen|author = Vinson, Greg|year = 2008|work = HydrogenTwo.com|publisher = |accessdate = January 14, 2012|archive-date = 2012-01-10|archive-url = https://web.archive.org/web/20120110195815/http://hydrogentwo.com/hydrogen-halogen.html|dead-url = yes}}</ref> di atas litium dan fluor sekaligus (muncul dua kali),<ref name="chemistry-international" /> atau di kiri mengambang di atas unsur-unsur lainnya dan tidak dimasukkan ke dalam golongan manapun<ref name="chemistry-international">{{cite journal |last1 = Kaesz|first1 = Herb|last2 = Atkins|first2 = Peter|date = November–December 2003|title = A Central Position for Hydrogen in the Periodic Table|journal = Chemistry International|volume = 25|issue = 6|pages = 14|publisher = [[International Union of Pure and Applied Chemistry]]|url = http://www.iupac.org/publications/ci/2003/2506/ud.html|accessdate = January 19, 2012}}</ref> dalam [[tabel periodik]].