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Baris 1:
{{Periodic table (micro)| title=Periode 1 dalam [[tabel periodik]] | mark=H,He}}
'''Unsur periode 1''' adalah [[Unsur kimia|unsur-unsur kimia]] dalam baris (atau [[periode tabel periodik|periode]]) pertama dari [[tabel periodik|tabel periodik unsur kimia]]. Tabel periodik disusun berdasarkan baris untuk menggambarkan keberulangan tren (periodik) perilaku kimia unsur-unsur seiring dengan kenaikan nomor atom. Baris baru dimulai ketika perilaku kimia mulai berulang, artinya unsur-unsur dengan perilaku yang sama akan jatuh pada kolom vertikal yang sama.

Periode pertama1 mengandung lebih sedikit unsur daripada baris-barisperiode lain dalam tabel, dengan hanya dua2 anggota yaitu: [[Hidrogenasi|hidrogen]] dan [[helium]]. Situasi ini dapat dijelakan menggunakan teori modern [[struktur atom]]. Dalam penjelasan [[mekanika kuantum]] tentang struktur [[atom]], periode ini berhubungan dengan pengisian [[Blok-s|orbital 1s]]. Unsur-unsur periode 1 mematuhi kaidah duet yang menyatakan bahwa mereka memerlukan dua [[elektron]] untuk melengkapi [[Kulitkulit valensi|kulit valensinya]]nya. Jumlah maksimum elektron yang dapat diakomodasi oleh unsur-unsur ini adalah dua, yang keduanya terletak di dalam orbital 1s. Oleh karena itu, periode 1 hanya beranggotakan dua unsur.
 
==Tren periodik==
== Tren periodik ==
{{double image|right|Electron shell 001 Hydrogen (diatomic nonmetal) - no label.svg|100|Electron shell 002 Helium - no label.svg|100|[[Hidrogen]]|[[Helium]]|Hydrogen's electron configuration is 1.|Helium's electron configuration is 2.}}
 
Semua periode lain dalam tabel periode mengandung sekurang-kurangnya 8 unsur, dan seringkalisering kali membantu menjelaskan [[tren periodik]] sepanjang periode. Namun, periode 1 hanya beranggotakan dua unsur, sehingga konsep ini tdaktidak berlaku di sini.
 
Dalam hal tren vertikal sepanjang golongan, helium dapat dipandang sebagai [[gas mulia]] yang berada di puncak [[Unsur golongan 18|Golongan 18]], tetapi sesuai dengan diskusi di bawah, kimia hidrogen bersifat unik dan tidak mudah dimasukkan ke dalam golongan manapun.
 
== Posisi unsur-unsur periode 1 dalam tabel periodik ==
Dalam hal tren vertikal sepanjang golongan, helium dapat dipandang sebagai [[gas mulia]] yang berada di puncak [[Unsur golongan 18|Golongan 18]], tetapi sesuai dengan diskusi di bawah, kimia hidrogen bersifat unik dan tidak mudah dimasukkan ke dalam golongan manapun.
Meskipun baik hidrogen dan helium berada dalam [[blok-s]], mereka berdua tidak berperilaku yang sama dengan unsur-unsur blok-s lainnya. Perilaku keduanya sangat berbeda dibandingkan unsur-unsur blok-s lainnya hingga memunculkan semacam polemik tentang peletakan kedua unsur ini dalam tabel periodik.
==Posisi unsur-unsur periode 1 dalam tabel periodik==
Meskipun baik hidrogen dan helium berada dalam [[blok-s]], mereka berdua tidak berperilaku yang sama dengan unsur-unsur blok-s lainnya. Perilaku keduanya sangat berbeeda dibandingkan unsur-unsur blok-s lainnya hingga memunculkan semacam polemik tentang peletakan kedua unsur ini dalam tabel periodik.
 
[[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]].
 
[[Helium]] hampir selalu diletakkan di atas [[neon]] (yang merupakan anggota [[blok-p]]) dalam tabel periodik sebagai [[gas mulia]],<ref name="iupac">{{cite web|url = http://old.iupac.org/reports/periodic_table/|title = International Union of Pure and Applied Chemistry > Periodic Table of the Elements|publisher = IUPAC|accessdate = 2011-05-01}}</ref> meskipun ia kadang-kadang diletakkan di atas [[berilium]] karena kesamaan konfigurasi elektronnya.<ref name="janet-table">{{cite web |url = http://www.webelements.com/nexus/Janet_Periodic_Table|title = Janet periodic table|author = Winter, Mark|date = 1993–2011|work = WebElements|accessdate = January 19, 2012|archive-date = 2012-04-06|archive-url = https://web.archive.org/web/20120406075222/http://www.webelements.com/nexus/Janet_Periodic_Table|dead-url = yes}}</ref>
== Unsur ==
{| class="wikitable"
 
Baris 36 ⟶ 40:
|}
 
=== Hidrogen ===
{{Main|Hidrogen}}
[[Berkas:Hydrogen_discharge_tube.jpg|leftkiri|thumbjmpl|150x150px|Tabung pembebas hidrogen]]
[[Berkas:Deuterium_discharge_tube.jpg|leftkiri|thumbjmpl|150x150px|Tabung pembebas deuterium]]
 
{{Unsur|Hidrogen|H|1}} Pada [[temperatur dan tekanan standar]], hidrogen tidak berwarna, tidak berbau, [[nonlogam]], tidak berasa, merupakan [[gas]] [[diatomik]] yang sangat [[Pembakaran|mudah terbakar]] dengan [[rumus molekul]] H<sub>2</sub>. Dengan [[massa atom]] 1,00794 [[Satuan massa atom|amu]], hidrogen adalah unsur paling ringan.<ref>{{cite web|accessdate = 2008-07-15|url = http://www.eia.doe.gov/kids/energyfacts/sources/IntermediateHydrogen.html|title = Hydrogen – Energy|publisher = Energy Information Administration}}</ref>
Baris 47 ⟶ 51:
[[Isotop]] hidrogen yang paling banyak terdapat di alam, diketahui sebagai [[Hidrogen-1|protium]], memiliki satu [[proton]] tanpa [[neutron]].<ref>{{cite news|title = Fusion Power Is Still Facing Formidable Difficulties|work = The New York Times|date = 1971-03-11|author = Sullivan, Walter}}</ref> Dalam senyawa ionik, ia dapat bermuatan positif, menjadi [[kation]] yang merupakan proton telanjang, atau bermuatan negatif, menjadi [[anion]] yang dikenal sebagai [[hidrida]]. Hidrogen dapat membentuk senyawa dengan sebagian besar unsur dan terdapat dalam [[air]] serta sebagian besar [[senyawa organik]].<ref>{{cite encyclopedia|encyclopedia = [[Encyclopædia Britannica]]|year = 2008|title = hydrogen}}</ref> Ia memainkan peran yang sangat penting dalam [[Teori reaksi asam-basa|kimia asam-basa]], di mana banyak reaksi terlibat pertukaran proton antar molekul yang dapat larut.<ref>{{cite journal|title = Electron-Driven Acid-Base Chemistry: Proton Transfer from Hydrogen Chloride to Ammonia|date = 2008-02-15|volume = 319|issue = 5865|pages = 936–939|doi = 10.1126/science.1151614|author = Eustis, S. N.|journal = Science|pmid = 18276886|last2 = Radisic|first2 = D|last3 = Bowen|first3 = KH|last4 = Bachorz|first4 = RA|last5 = Haranczyk|first5 = M|last6 = Schenter|first6 = GK|last7 = Gutowski|first7 = M|bibcode = 2008Sci...319..936E}}</ref> Karena hanya atom netral yang dapat dianalisis menggunakan [[persamaan Schrödinger]], studi energetika dan [[Spektrum atom|spektrum]] atom hidrogen memainkan peran kunci dalam pengembangan [[mekanika kuantum]].<ref>{{cite encyclopedia|encyclopedia = [[Encyclopædia Britannica]]|year = 2008|title = Time-dependent Schrödinger equation}}</ref>
 
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&nbsp;— 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|url = https://archive.org/details/sim_materials-science-and-engineering_1988-03_99/page/457|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|url = https://archive.org/details/sim_progress-in-materials-science_1988_32_4/page/262|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>|jmpl|kiri|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 PerancisPrancis [[Pierre_JanssenPierre 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|archive-date = 2009-10-29|archive-url = https://web.archive.org/web/20091029133529/http://encarta.msn.com/encyclopedia_762508746/Pierre_Janssen.html|dead-url = yes}}</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|archive-date = 2008-07-25|archive-url = https://web.archive.org/web/20080725060842/http://www.blm.gov/wo/st/en/info/newsroom/2007/january/NR0701_2.html|dead-url = yes}}</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 nampaktampak 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>
 
Helium adalah unsur kedua terringan dan merupakan unsur kedua paling melimpah yang teramati di alam semesta.<ref>{{Cite web|url = http://www.webelements.com/helium/geology.html|website = WebElements|title = Helium: geological information}}</ref> Sebagian besar helium terbentuk selama Ledakan Dahsyat, tetapi helium baru terbentuk sebagai hasil fusi nuklir hidrogen di dalam bintang.<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
<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 />
|work=New Scientist|date=1990-02-03|author=Cox, Tony}}</ref> Di bumi, helium relatif langka dan tercipta dari peluruhan alami beberapa unsur radioaktif<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> karena partikel alfa yang dipancarkan mengandung inti helium. Helium radiogenik terperangkap dalam gas alam pada konsentrasi sampai dengan tujuh persen 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> yang diekstraksi secara komersial dengan cara proses pemisahan temperatur rendah yang disebut distilasi fraksi.<ref>{{cite news|title=Where Do We Get the Helium We Use?|publisher=The Science Teacher|date=2006-12-01|author=Voth, Greg}}</ref>
 
== UnsurPeran biologis ==
[[Hidrogen]] adalah unsur esensial bagi kehidupan. Ia ada dalam air dan dalam hampir semua molekul makhluk hidup. Namun, hidrogen sebagai unsur maupun molekul diatomiknya tidak memainkan peran aktif tertentu. Ia berada dalam ikatan dengan atom [[karbon]] dan [[oksigen]], sementara kimia dalam kehidupan lebih menekankan pada lokus-lokus aktif yang melibatkan, misalnya, [[oksigen]], [[nitrogen]], dan [[fosforus]].<ref>{{cite web|url=http://www.rsc.org/periodic-table/element/1/hydrogen|title=Hydrogen|website=Periodic Table|publisher=Royal Society of Chemistry|accessdate=2016-02-11}}</ref>
{| 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>
|}
 
[[Helium]] tidak diketahui memiliki peran biologis. Helium tak beracun.<ref>{{cite web|url=http://www.rsc.org/periodic-table/element/2/helium|title=Helium|website=Periodic Table|publisher=Royal Society of Chemistry|accessdate=2016-02-11}}</ref>
=== 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]]
 
== Tabel unsur ==
Helium (He) adalah unsur kimia [[monoatomik]] tak berasa dan tak berwarna. Helium ditemukan pada 1868 oleh astronom Perancis [[Pierre Janssen]].
{{Tabel periodik (periode 1)}}
{{br}}
 
== Referensi ==
{{Reflist|2}}
 
== Lihat juga ==
* [[Periode tabel periodik]]
** [[Unsur periode 2]]
** [[Unsur periode 3]]
** [[Unsur periode 4]]
** [[Unsur periode 5]]
** [[Unsur periode 6]]
** [[Unsur periode 7]]
** [[Tabel periodik perluasan|Unsur periode 8]]
* [[Golongan tabel periodik]]
* [[Tabel periodik]]
 
== Bacaan tambahan ==
{{Wikipedia books|PeriodUnsur-unsur 1Periode elements1}}
* {{cite book
|author=Bloch, D. R.
|year=2006
|title=Organic Chemistry Demystified
|url=http://books.google.com/?id=yVPcSIn5xjAC
|publisher=McGraw-Hill Professional
|isbn=0-07-145920-0
|ref=CITEREFBloch2006
}}
{{kimia-stubartikel bagus}}
{{DEFAULTSORT:Periode 01}}
[[Kategori:Periode dalam tabel periodik]]
<!--
 
 
 
{{clear}}
 
==Elements==
{| class="wikitable"
|-
! colspan="3" | [[Chemical element]] !! [[Chemical series]] !! [[Electron configuration]]
|- style="background-color: {{element color|diatomic nonmetal}}"
| 1 || '''H''' || [[Hydrogen]] || [[Diatomic nonmetal]] || 1s<sup>1</sup>
|- style="background-color: #c0ffff"
| 2 || '''He''' || [[Helium]] || [[Noble gas]] || 1s<sup>2</sup>
|}
 
===Hydrogen===
{{Main|Hydrogen}}
[[File:Hydrogen discharge tube.jpg|thumb|left|150px|Hydrogen discharge tube]]
[[File:Deuterium discharge tube.jpg|thumb|left|150px|Deuterium discharge tube]]
 
Hydrogen (H) is the [[chemical element]] with [[atomic number]] 1. At [[standard temperature and pressure]], hydrogen is a colorless, odorless, [[nonmetal]]lic, tasteless, highly [[combustion|flammable]] [[Diatomic molecule|diatomic]] [[gas]] with the [[molecular formula]] H<sub>2</sub>. With an [[atomic mass]] of 1.00794&nbsp;amu, hydrogen is the lightest element.<ref>{{cite web|accessdate=2008-07-15|url=http://www.eia.doe.gov/kids/energyfacts/sources/IntermediateHydrogen.html|title=Hydrogen – Energy |publisher=Energy Information Administration}}</ref>
 
Hydrogen is the most [[abundance of the chemical elements|abundant]] of the chemical elements, constituting roughly 75% of the universe's elemental mass.<ref>{{cite web | last=Palmer | first=David | date=November 13, 1997 | url=http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/971113i.html | title=Hydrogen in the Universe | publisher=NASA | accessdate=2008-02-05}}</ref> [[Star]]s in the [[main sequence]] are mainly composed of hydrogen in its [[plasma (physics)|plasma]] state. Elemental hydrogen is relatively rare on [[Earth]], and is industrially produced from [[hydrocarbon]]s such as methane, after which most elemental hydrogen is used "captively" (meaning locally at the production site), with the largest markets almost equally divided between [[fossil fuel]] upgrading, such as [[hydrocracking]], and [[ammonia]] production, mostly for the fertilizer market. Hydrogen may be produced from water using the process of [[electrolysis]], but this process is significantly more expensive commercially than hydrogen production from natural gas.<ref>{{cite web | author=Staff | year=2007 | url=http://www.fsec.ucf.edu/en/consumer/hydrogen/basics/production.htm | title=Hydrogen Basics&nbsp;— Production | publisher=Florida Solar Energy Center | accessdate=2008-02-05}}</ref>
 
The most common naturally occurring [[isotope]] of hydrogen, known as [[hydrogen-1|protium]], has a single [[proton]] and no [[neutron]]s.<ref>{{cite news|title=Fusion Power Is Still Facing Formidable Difficulties|work=The New York Times|date=1971-03-11|author=Sullivan, Walter}}</ref> In [[ionic compound]]s, it can take on either a positive charge, becoming a [[Ion|cation]] composed of a bare proton, or a negative charge, becoming an [[Ion|anion]] known as a [[hydride]]. Hydrogen can form compounds with most elements and is present in [[water]] and most [[organic compound]]s.<ref>{{cite encyclopedia|encyclopedia=[[Encyclopædia Britannica]]|year=2008|title=hydrogen}}</ref> It plays a particularly important role in [[acid-base reaction theories|acid-base chemistry]], in which many reactions involve the exchange of protons between soluble molecules.<ref>{{cite journal|title=Electron-Driven Acid-Base Chemistry: Proton Transfer from Hydrogen Chloride to Ammonia|date=2008-02-15|volume=319|issue=5865|pages=936–939|doi=10.1126/science.1151614|author=Eustis, S. N.|journal=Science|pmid=18276886|last2=Radisic|first2=D|last3=Bowen|first3=KH|last4=Bachorz|first4=RA|last5=Haranczyk|first5=M|last6=Schenter|first6=GK|last7=Gutowski|first7=M|bibcode = 2008Sci...319..936E }}</ref> As the only neutral atom for which the [[Schrödinger equation]] can be solved analytically, study of the energetics and [[atomic spectrum|spectrum]] of the hydrogen atom has played a key role in the development of [[quantum mechanics]].<ref>{{cite encyclopedia|encyclopedia=[[Encyclopædia Britannica]]|year=2008|title= Time-dependent Schrödinger equation}}</ref>
 
The interactions of hydrogen with various metals are very important in [[metallurgy]], as many metals can suffer [[hydrogen embrittlement]],<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> and in developing safe ways to store it for use as a fuel.<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&nbsp;— 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> Hydrogen is highly soluble in many compounds composed of [[Rare earth element|rare earth metals]] and [[transition metal]]s<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> and can be dissolved in both [[crystalline]] and [[amorphous solid|amorphous]] metals.<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> Hydrogen solubility in metals is influenced by local distortions or impurities in the metal [[crystal lattice]].<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>
 
===Helium===
{{Main|Helium}}
[[File:Helium discharge tube.jpg|left|thumb|upright|150px|Helium discharge tube]]
 
Helium (He) is a colorless, odorless, tasteless, non-toxic, [[inert]] [[monatomic]] chemical element that heads the [[noble gas]] series in the [[periodic table]] and whose [[atomic number]] is 2.<ref>{{cite web|accessdate=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|accessdate=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|accessdate=2008-07-15|url=http://encarta.msn.com/encyclopedia_762508746/pierre_janssen.html|title=Pierre Janssen |publisher=MSN Encarta}}</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|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> 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|accessdate=2008-07-15|url=http://www.howstuffworks.com/helium.htm|title=How Helium Balloons Work |publisher=How Stuff Works|author=Brain, Marshall}}</ref> for providing lift in [[airship]]s,<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> 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|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> 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|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> 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|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]]s.<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]]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|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>
 
==References==
{{Reflist|2}}
 
==Further reading==
{{Wikipedia books|Period 1 elements}}
* {{cite book
|author=Bloch, D. R.
|year=2006
|title=Organic Chemistry Demystified
|url=http://books.google.com/?id=yVPcSIn5xjAC
|publisher=McGraw-Hill Professional
|isbn=0-07-145920-0
|ref=CITEREFBloch2006
}}
 
{{Compact periodic table}}
{{Navbox periodic table}}
 
{{DEFAULTSORT:Periode 01}}
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[[Kategori:Periode unsur kimia]]
 
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