Editing Period 1 element (section)

===Helium===
{{Main|Helium}}
[[File:Helium discharge tube.jpg|thumb|upright|150px|Helium discharge tube]]

Helium (He) is a colorless, odorless, tasteless, non-toxic, [[Inert gas|inert]] [[monatomic]] chemical element that heads the [[noble gas]] series in the [[periodic table]] and whose [[atomic number]] is 2.<ref>{{cite web|access-date=2008-07-15|url=http://www.webelements.com/helium/|title=Helium: the essentials |publisher=WebElements}}</ref> Its [[boiling point|boiling]] and [[melting point|melting]] points are the lowest among the elements and it exists only as a [[gas]] except in extreme conditions.<ref>{{cite web|access-date=2008-07-15|url=http://www.webelements.com/helium/physics.html|title=Helium: physical properties |publisher=WebElements}}</ref>

Helium was discovered in 1868 by French astronomer [[Pierre Janssen]], who [[discovery of the chemical elements|first detected]] the substance as an unknown yellow [[spectroscopy|spectral line]] signature in light from a [[solar eclipse]].<ref>{{cite web|access-date=2008-07-15|url=http://encarta.msn.com/encyclopedia_762508746/pierre_janssen.html|title=Pierre Janssen|publisher=MSN Encarta|url-status=dead|archive-url=https://web.archive.org/web/20091029133529/http://encarta.msn.com/encyclopedia_762508746/Pierre_Janssen.html|archive-date=2009-10-29}}</ref> In 1903, large reserves of helium were found in the [[natural gas field]]s of the United States, which is by far the largest supplier of the gas.<ref>{{cite web|access-date=2008-07-15|url=http://www.blm.gov/wo/st/en/info/newsroom/2007/january/NR0701_2.html|title=Where Has All the Helium Gone?|publisher=Bureau of Land Management|date=2007-01-18|author=Theiss, Leslie|url-status=dead|archive-url=https://web.archive.org/web/20080725060842/http://www.blm.gov/wo/st/en/info/newsroom/2007/january/NR0701_2.html|archive-date=2008-07-25}}</ref> The substance is used in [[cryogenics]],<ref>{{cite book|title=Cryogenic Engineering: Fifty Years of Progress|author=Timmerhaus, Klaus D.|date=2006-10-06|publisher=Springer|isbn=0-387-33324-X}}</ref> in deep-sea breathing systems,<ref>{{cite journal|title=Helium voice unscrambling|author=Copel, M.|journal=Audio and Electroacoustics|volume=14|issue=3|date=September 1966|pages=122–126|doi=10.1109/TAU.1966.1161862}}</ref> to cool [[superconducting magnet]]s, in [[helium dating]],<ref>{{cite encyclopedia|encyclopedia=[[Encyclopædia Britannica]]|year=2008|title=helium dating}}</ref> for inflating [[balloon]]s,<ref>{{cite web|access-date=2008-07-15|url=http://www.howstuffworks.com/helium.htm|title=How Helium Balloons Work |publisher=How Stuff Works|author=Brain, Marshall|date=April 2000 }}</ref> for providing lift in [[airship]]s,<ref>{{cite web|access-date=2008-07-15|url=http://www.popsci.com/military-aviation-space/article/2008-07/return-blimp|title= The Return of the Blimp |work=Popular Science|date=2008-07-10|author=Jiwatram, Jaya}}</ref> and as a protective gas for industrial uses such as [[arc welding]] and growing [[silicon]] wafers.<ref>{{cite journal|title=When good GTAW arcs drift; drafty conditions are bad for welders and their GTAW arcs.|journal=Welding Design & Fabrication|date=2005-02-01}}</ref> Inhaling a small [[volume]] of the gas temporarily changes the timbre and quality of the human voice.<ref>{{cite web|access-date=2008-07-15|url=http://www.sciam.com/article.cfm?id=why-does-inhaling-helium|title=Why does inhaling helium make one's voice sound strange? |work=Scientific American|date=2006-09-04|author=Montgomery, Craig}}</ref> The behavior of liquid helium-4's two fluid phases, helium I and helium II, is important to researchers studying [[quantum mechanics]] and the phenomenon of [[superfluidity]] in particular,<ref>{{cite web|access-date=2008-07-15|url=https://www.sciencedaily.com/releases/2004/09/040903085531.htm|title=Probable Discovery Of A New, Supersolid, Phase Of Matter |publisher=Science Daily|date=2004-09-03}}</ref> and to those looking at the effects that temperatures near [[absolute zero]] have on [[matter]], such as with [[superconductivity]].<ref>{{cite news|title=Scientists See Peril In Wasting Helium; Scientists See Peril in Waste of Helium|work=The New York Times|date=1979-08-21|author= Browne, Malcolm W.}}</ref>

Helium is the second lightest element and is the second most [[chemical abundance|abundant]] in the observable universe.<ref>{{cite web|access-date=2008-07-15|url=http://www.webelements.com/helium/geology.html|title=Helium: geological information |publisher=WebElements}}</ref> Most helium was formed during the [[Big Bang]], but new helium is being created as a result of the [[nuclear fusion]] of hydrogen in [[star]]s.<ref>{{cite web|access-date=2008-07-15|url=https://www.newscientist.com/article/mg12517027.000-origin-of-the-chemical-elements.html|title=Origin of the chemical elements
|work=New Scientist|date=1990-02-03|author=Cox, Tony}}</ref> On [[Earth]], helium is relatively rare and is created by the natural [[radioactive decay|decay]] of some radioactive elements<ref>{{cite news|title=Helium supply deflated: production shortages mean some industries and partygoers must squeak by.|publisher=Houston Chronicle|date=2006-11-05}}</ref> because the [[alpha particle]]s that are emitted consist of helium [[atomic nucleus|nuclei]]. This radiogenic helium is trapped with [[natural gas]] in concentrations of up to seven percent by volume,<ref>{{cite web|access-date=2008-07-15|url=http://www.aapg.org/explorer/2008/02feb/helium.cfm|title=Helium a New Target in New Mexico |publisher=American Association of Petroleum Geologists|date=2008-02-02|author=Brown, David}}</ref> from which it is extracted commercially by a low-temperature separation process called [[fractional distillation]].<ref>{{cite news|title=Where Do We Get the Helium We Use?|publisher=The Science Teacher|date=2006-12-01|author=Voth, Greg}}</ref>