Editing Period 6 element (section)

===Polonium===
{{main|Polonium}}
'''Polonium''' is a [[chemical element]] with the symbol '''Po''' and [[atomic number]] 84, discovered in 1898 by [[Marie Curie|Marie Skłodowska-Curie]] and [[Pierre Curie]]. A rare and highly [[radioactive]] element, polonium is chemically similar to [[bismuth]]<ref>{{cite web| url = http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/Po.html |title = Polonium| access-date = 2009-05-05}}</ref> and [[tellurium]], and it occurs in [[uranium]] [[ore]]s. Polonium has been studied for possible use in heating [[spacecraft]]. As it is unstable, all [[isotopes of polonium]] are radioactive. There is disagreement as to whether polonium is a [[post-transition metal]] or [[metalloid]].<ref>{{cite journal| doi=10.1021/ed100308w |title = Polonium and Astatine Are Not Semimetals|journal= Journal of Chemical Education| year=2010| last1=Hawkes| first1=Stephen J.| volume=87| issue=8| pages=783 |bibcode = 2010JChEd..87..783H }}</ref><ref>{{cite web |url=http://periodic.lanl.gov/metal.shtml |title=Characterizing the Elements |author=<!--Staff writer(s); no by-line.--> |publisher=[[Los Alamos National Laboratory]] |access-date=4 March 2013}}</ref>