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Interaksi hidrogen dengan berbagai logam sangat penting dalam [[metalurgi]], karena banyak logam dapat mengalami [[perapuhan hidrogen]],<ref>{{cite journal |last = Rogers|first = H. C.|title = Hydrogen Embrittlement of Metals|journal = Science|year = 1999|volume = 159|issue = 3819|pages = 1057–1064|doi = 10.1126/science.159.3819.1057|pmid = 17775040|bibcode = 1968Sci...159.1057R}}</ref> dan dalam pengembangan cara aman penyimpanannya sebagai bahan bakar.<ref>{{cite news |last = Christensen|first = C. H.|author2 = Nørskov, J. K.|author3 = Johannessen, T.|date = July 9, 2005|title = Making society independent of fossil fuels — Danish researchers reveal new technology|publisher = Technical University of Denmark|url = http://www.dtu.dk/English/About_DTU/News.aspx?guid=%7BE6FF7D39-1EDD-41A4-BC9A-20455C2CF1A7%7D|accessdate = 2008-03-28}}</ref> Hidrogen sangat mudah larut dalam banyak senyawa yang tersusun oleh [[logam tanah jarang]] dan [[logam transisi]]<ref name="Takeshita">{{cite journal |last = Takeshita|first = T.|author2 = Wallace, W.E.|author3 = Craig, R.S.|title = Hydrogen solubility in 1:5 compounds between yttrium or thorium and nickel or cobalt|journal = Inorganic Chemistry|year = 1974|volume = 13|issue = 9|pages = 2282–2283|doi = 10.1021/ic50139a050}}</ref> serta dapat larut dalam logam baik [[kristal]] maupun [[Padatan amorf|amorf]].<ref name="Kirchheim1">{{cite journal |last = Kirchheim|first = R.|author2 = Mutschele, T.|author3 = Kieninger, W|title = Hydrogen in amorphous and nanocrystalline metals|journal = Materials Science and Engineering|year = 1988|volume = 99|pages = 457–462|doi = 10.1016/0025-5416(88)90377-1}}</ref> Kelarutan hidrogen dalam logam mempengaruhi distorsi lokal atau ketidakmurnian [[kisi kristal]] logam.<ref name="Kirchheim2">{{cite journal |last = Kirchheim|first = R.|title = Hydrogen solubility and diffusivity in defective and amorphous metals|journal = Progress in Materials Science|year = 1988|volume = 32|issue = 4|pages = 262–325|doi = 10.1016/0079-6425(88)90010-2}}</ref>
<h3 />===Helium===
{{Main|Helium}}
<figure class="mw-halign-left">[./Berkas:Helium_discharge_tube.jpg [[Berkas:Helium_discharge_tube.jpg|link=|150x150px]]]<figcaption>|thumb|left|Tabung pembebas helium</figcaption></figure>]]
<p>{{Unsur|Helium|He|2}} Helium adalah bahan kimia tak berwarna, tak berbau, tak berasa, tak beracun, [[monoatomik]] [[inert]] dan merupakan [[gas mulia]] pertama dalam [[tabel periodik]].<ref>{{cite web|accessdate = 2008-07-15|url = http://www.webelements.com/helium/|title = Helium: the essentials|publisher = WebElements}}</ref> Titik [[Titik lebur|lebur]] dan [[Titik didih|didihnya]] adalah yang paling rendah dibandingkan unsur-unsur lainnya dan hanya terdapat dalam bentuk [[gas]] kecuali dalam kondisi ekstrem.<ref>{{cite web|accessdate = 2008-07-15|url = http://www.webelements.com/helium/physics.html|title = Helium: physical properties|publisher = WebElements}}</ref></p>
<p>Helium pertama kali ditemukan pada tahun 1868 oleh astronom Perancis [[Pierre_Janssen]], yang [[Penemuan unsur kimia|pertama kali]] mendeteksi zat sebagai tanda [[Spektroskopi|garis spektrum]] kuning tak diketahui dalam cahaya dari [[gerhana matahari]].<ref>{{cite web|accessdate = 2008-07-15|url = http://encarta.msn.com/encyclopedia_762508746/pierre_janssen.html|title = Pierre Janssen|publisher = MSN Encarta}}</ref> Pada tahun 1903, cadangan helium yang besar ditemukan dalam [[ladang gas alam]] di Amerika Serikat, yang dikenal sebagai pemasok gas terbesar.<ref>{{cite web|accessdate = 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}}</ref> Helium digunakan dalam [[kriogenik]],<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> sistem pernapasan laut-dalam<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>, untuk mendinginkan [[Magnet superkonduksi|magnet superkonduktor]], dan dalam [[Penanggalan Helium|penanggalan helium]],<ref>{{cite encyclopedia|encyclopedia = [[Encyclopædia Britannica]]|year = 2008|title = helium dating}}</ref> untuk pengisi [[balon]] udara,<ref>{{cite web|accessdate = 2008-07-15|url = http://www.howstuffworks.com/helium.htm|title = How Helium Balloons Work|publisher = How Stuff Works|author = Brain, Marshall}}</ref>, sebagai pengangkat [[kapal udara]],<ref>{{cite web|accessdate = 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> dan sebagai gas pelindung untuk penggunaan industri seperti [[Arc welding|pengelasan]] dan pengembangan wafer [[silikon]].<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> Menghirup [[Volume|sedikit]] gas ini akan mengubah sementara timbre dan kualitas suara manusia.<ref>{{cite web|accessdate = 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> Perilaku fasa dua fluida helium-4 cair, helium I dan helium II, penting bagi peneliti yang mempelajari [[mekanika kuantum]] dan terutama fenomena [[superfluiditas]],<ref>{{cite web|accessdate = 2008-07-15|url = http://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> dan hal tersebut nampak pada efek bahwa pada temperatur hampir [[nol mutlak]], materi mengalami [[superkonduktivitas]].<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></p>
<p>Helium is the second lightest element and is the second most [[Chemical abundance|abundant]] in the observable universe.<ref>{{cite web|accessdate = 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|stars]].<ref>{{cite web|accessdate = 2008-07-15|url = http://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|alpha particles]] 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|accessdate = 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></p><references />
== Unsur ==
{| class="wikitable"
|-
! colspan="3" | [[Unsur kimia]] !! [[Golongan tabel periodik|Golongan]] !! [[Konfigurasi elektron]]
|- style="background-color: {{element color|diatomic nonmetal}}"
| 1 || '''H''' || [[Hidrogen]] || [[Nonlogam diatomik]] || 1s<sup>1</sup>
|- style="background-color: #c0ffff"
| 2 || '''He''' || [[Helium]] || [[Gas mulia]] || 1s<sup>2</sup>
|}
=== Hidrogen ===
{{Main|Hidrogen}}
[[Berkas:Hydrogen discharge tube.jpg|thumb|left|150px]]
[[Berkas:Deuterium discharge tube.jpg|thumb|left|150px]]
Hidrogen (H) adalah [[unsur kimia]] dengan [[nomor atom]] 1.
{{br}}
=== Helium ===
{{Main|Helium}}
[[Berkas:Helium discharge tube.jpg|left|thumb|upright|150px]]
Helium (He) adalah unsur kimia [[monoatomik]] tak berasa dan tak berwarna. Helium ditemukan pada 1868 oleh astronom Perancis [[Pierre Janssen]].
{{br}}
== Referensi ==
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