View source for Physics:Isotopes of hydrogen

{{Short description|Hydrogen with different numbers of neutrons}}
{{infobox hydrogen isotopes}}

[[Chemistry:Hydrogen|Hydrogen]] (<sub>1</sub>H) has three naturally occurring [[Physics:Isotope|isotope]]s, sometimes denoted {{SimpleNuclide|Hydrogen|1}}, {{SimpleNuclide|Hydrogen|2}}, and {{SimpleNuclide|Hydrogen|3}}. {{SimpleNuclide|Hydrogen|1}} and {{SimpleNuclide|Hydrogen|2}} are stable, while {{SimpleNuclide|Hydrogen|3}} has a [[Physics:Half-life|half-life]] of {{val|12.32|(2)}} years.<ref name=NUBASE2020a>{{Cite journal |last1=Kondev |first1=F. G. |last2=Wang |first2=M. |last3=Huang |first3=W. J. |last4=Naimi |first4=S. |last5=Audi |first5=G. |date=March 2021 |title=The NUBASE2020 evaluation of nuclear physics properties \ast|journal=Chinese Physics C |language=en |volume=45 |issue=3 |pages=030001 |doi=10.1088/1674-1137/abddae |bibcode=2021ChPhC..45c0001K |s2cid=233794940 |issn=1674-1137|doi-access=free}}</ref>{{refn|group=nb|name=NUBASE2020 tropical year|Note that NUBASE2020 uses the [[Astronomy:Tropical year|tropical year]] to convert between years and other units of time, not the Gregorian year. The relationship between years and other time units in NUBASE2020 is as follows: {{nowrap|1=1 y = 365.2422 d = 31 556 926 s}} }} Heavier isotopes also exist, all of which are synthetic and have a half-life of less than one [[Orders of magnitude (time)#Zeptosecond|zeptosecond]] (10<sup>−21</sup>&nbsp;s).<ref>{{cite journal
 |author=Y. B. Gurov|year=2004
 |title=Spectroscopy of superheavy hydrogen isotopes in stopped-pion absorption by nuclei
 |journal=Physics of Atomic Nuclei
 |volume=68 |issue=3 |pages=491–497
 |bibcode = 2005PAN....68..491G
 |doi=10.1134/1.1891200
 |s2cid=122902571
 |display-authors=0}}</ref><ref name="Korsheninnikov">
{{cite journal
 |author=A. A. Korsheninnikov|year=2003
 |title=Experimental Evidence for the Existence of <sup>7</sup>H and for a Specific Structure of <sup>8</sup>He
 |journal=[[Physics:Physical Review Letters|Physical Review Letters]]
 |volume=90 |issue=8 |pages=082501
 |bibcode=2003PhRvL..90h2501K
 |doi=10.1103/PhysRevLett.90.082501
 |display-authors=0 |pmid=12633420}}</ref>
Of these, {{SimpleNuclide|Hydrogen|5}} is the least stable, while {{SimpleNuclide|Hydrogen|7}} is the most.

Hydrogen is the only [[Chemistry:Chemical element|element]] whose isotopes have different names that remain in common use today: the {{SimpleNuclide|Hydrogen|2}} (or hydrogen-2) isotope is [[Physics:Deuterium|deuterium]]<ref>{{GoldBookRef|file=D01648|title=deuterium}}</ref> and the {{SimpleNuclide|Hydrogen|3}} (or hydrogen-3) isotope is [[Physics:Tritium|tritium]].<ref>{{GoldBookRef|file=T06513|title=tritium}}</ref> The symbols D and T are sometimes used for deuterium and tritium. The [[Organization:International Union of Pure and Applied Chemistry|IUPAC]] accepts the D and T symbols, but recommends using standard isotopic symbols ({{SimpleNuclide|Hydrogen|2}} and {{SimpleNuclide|Hydrogen|3}}) instead to avoid confusion in the alphabetic sorting of [[Chemistry:Chemical formula|chemical formula]]s.<ref>{{RedBook2005|page=48}}</ref> The isotope {{SimpleNuclide|Hydrogen|1}}, with no [[Physics:Neutron|neutron]]s, is sometimes called [[Physics:Hydrogen atom|protium]].<ref>{{GoldBookRef|file=P04903|title=protium}}</ref> (During the early study of radioactivity, some other heavy radioactive isotopes were given [[Chemistry:Chemical symbol#Symbols for named isotopes|names]], but such names are rarely used today.)

[[File:Hydrogen Deuterium Tritium Nuclei Schmatic-en.svg|thumb |upright=1.8|left|The three most stable isotopes of hydrogen: protium (''[[Chemistry:Mass number|A]]''&nbsp;=&nbsp;1), deuterium (''A''&nbsp;=&nbsp;2), and tritium (''A''&nbsp;=&nbsp;3).]]
{{clear}}
==List of isotopes==
Note that "y" means "year", but "ys" means "yoctosecond" (10<sup>−24</sup> second).
{{Isotopes table
|symbol=H
|refs=NUBASE2020, AME2020 II
|notes=mass#, unc(), var[], spin#, spin(), daughter-st, n, note
}}
|-
| {{SimpleNuclide|Hydrogen|1}}
| 1
| 0
| {{val|1.007825031898|(14)}}
| colspan=3 align=center|'''Stable'''<ref group="n">Unless [[Physics:Proton decay|proton decay]] occurs.</ref><ref group="n">This and '''{{SimpleNuclide|Helium|3}}''' are the only stable nuclides with more protons than neutrons.</ref>
| 1/2+
| colspan="2" style="text-align:center" | [{{val|0.99972}}, {{val|0.99999}}]<ref name="Atomic Weight of Hydrogen">{{Cite web|title=Atomic Weight of Hydrogen|url=http://ciaaw.org/hydrogen.htm|access-date=24 June 2021|website=CIAAW}}</ref>
| Protium
|-
| [[Physics:Deuterium|<sup>2</sup>H]] (D)<ref group="n">Produced during [[Astronomy:Big Bang nucleosynthesis|Big Bang nucleosynthesis]].</ref><ref group="n">One of the few stable [[Physics:Even and odd atomic nuclei#Odd proton, odd neutron|odd-odd nuclei]]</ref>
| 1
| 1
| {{val|2.014101777844|(15)}}
| colspan=3 align=center |'''Stable'''
| 1+
| colspan="2" style="text-align:center" | [{{val|0.00001}}, {{val|0.00028}}]<ref name="Atomic Weight of Hydrogen" />
| Deuterium
|-
| [[Physics:Tritium|<sup>3</sup>H]] (T)<ref group="n">Produced during Big Bang nucleosynthesis, but not primordial, as all such atoms have since decayed to '''{{SimpleNuclide|Helium|3}}'''.</ref>
| 1
| 2
| {{val|3.016049281320|(81)}}
| {{val|12.32|(2)|u=y}}
| [[Physics:Beta decay|β<sup>−</sup>]]
| '''{{SimpleNuclide|Helium|3}}'''
| 1/2+
| Trace<ref group="n">Tritium occurs naturally as a [[Physics:Cosmogenic nuclide|cosmogenic nuclide]].</ref>
|
| Tritium

|-
| {{SimpleNuclide|Hydrogen|4}}
| 1
| 3
| {{val|4.02643|(11)}}
| {{val|139|(10)|ul=ys}}
| [[Physics:Neutron emission|n]]
| {{SimpleNuclide|Hydrogen|3}}
| 2−
|
|
|-
| {{SimpleNuclide|Hydrogen|5}}
| 1
| 4
| {{val|5.03531|(10)}}
| {{val|86|(6)|u=ys}}
| 2n
| {{SimpleNuclide|Hydrogen|3}}
| (1/2+)
|
|
|-
| rowspan=2|{{SimpleNuclide|Hydrogen|6}}
| rowspan=2|1
| rowspan=2|5
| rowspan=2|{{val|6.04496|(27)}}
| rowspan=2|{{val|294|(67)|u=ys}}
| n ?<ref group="n" name="decay mode 1">Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide.</ref>
| {{SimpleNuclide|Hydrogen|5}} ?
| rowspan=2|2−#
| rowspan=2|
| rowspan=2|
|-
| 3n ?<ref group="n" name="decay mode 1" />
| {{SimpleNuclide|Hydrogen|3}} ?
|-
| {{SimpleNuclide|hydrogen|7}}
| 1
| 6
| {{val|7.052750|(108)}}#
| {{val|652|(558)|u=ys}}
| 2n ?<ref group="n" name="decay mode 1" />
| {{SimpleNuclide|hydrogen|5}} ?
| 1/2+#
| 
| 
{{Isotopes table/footer}}

== Hydrogen-1 (protium) <span class="anchor" id="Hydrogen-1_(Protium)"></span>==
[[File:H-1 atom.png|thumb|right|Protium, the most common isotope of hydrogen, consists of one proton and one electron. Unique among all stable isotopes, it has no neutrons. (see diproton for a discussion of why others do not exist)]]{{Redirect|Protium}}
'''{{SimpleNuclide|Hydrogen|1}}''' (atomic mass {{val|1.007825031898|(14)|ul=Da}}) is the most common hydrogen isotope, with an abundance of more than 99.98%. Because the [[Physics:Atomic nucleus|nucleus]] of this isotope consists of only a single [[Physics:Proton|proton]], it is given the formal name '''protium'''.

The proton has never been observed to decay, and hydrogen-1 is therefore considered a stable isotope. Some [[Physics:Grand Unified Theory|grand unified theories]] proposed in the 1970s predict that [[Physics:Proton decay|proton decay]] can occur with a half-life between {{val|e=28}} and {{val|e=36}} years.<ref>{{cite web |title=Grand Unified Theories and Proton Decay |author=Ed Kearns |publisher=Boston University |date=2009 |page=15 |url=http://physics.bu.edu/NEPPSR/TALKS-2009/Kearns_GUTs_ProtonDecay.pdf}}</ref> If this prediction is found to be true, then hydrogen-1 (and indeed all nuclei now believed to be stable) are only observationally stable. {{As of|2018}}, experiments have shown that the minimum mean lifetime of the proton is in excess of {{val|3.6|e=29}} years.<ref>{{Cite journal |last1=The SNO+ Collaboration |last2=Anderson |first2=M. |last3=Andringa |first3=S. |last4=Arushanova |first4=E. |last5=Asahi |first5=S. |last6=Askins |first6=M. |last7=Auty |first7=D. J. |last8=Back |first8=A. R. |last9=Barnard |first9=Z. |last10=Barros |first10=N. |last11=Bartlett |first11=D. |date=2019-02-20 |title=Search for invisible modes of nucleon decay in water with the SNO+ detector |journal=Physical Review D |volume=99 |issue=3 |pages=032008 |doi=10.1103/PhysRevD.99.032008 |arxiv=1812.05552 |bibcode=2019PhRvD..99c2008A |s2cid=96457175 |doi-access=free}}</ref>

== Hydrogen-2 (deuterium) ==
{{Main|Physics:Deuterium}}
[[File:H-2 atom.png|250px|thumbnail|left|A deuterium atom contains one proton, one neutron, and one electron.]]
'''{{SimpleNuclide|Hydrogen|2}}''' (atomic mass {{val|2.014101777844|(15)|ul=Da}}), the other stable hydrogen isotope, is known as ''[[Physics:Deuterium|deuterium]]'' and contains one proton and one neutron in its nucleus. The nucleus of deuterium is called a deuteron. Deuterium comprises 0.0026–0.0184% (26&nbsp;ppm or 184&nbsp;ppm ; by population, not by mass) of hydrogen samples on Earth, with the lower number tending to be found in samples of hydrogen gas and the higher enrichment (0.015% or 150&nbsp;ppm) typical of ocean water. Deuterium on Earth has been enriched with respect to its initial concentration in the [[Astronomy:Big Bang|Big Bang]] and the outer solar system (about 27 ppm, by atom fraction) and its concentration in older parts of the Milky Way galaxy (about 0.0023%, or 23&nbsp;ppm). Presumably the differential concentration of deuterium in the inner solar system is due to the lower volatility of deuterium gas and compounds, enriching deuterium fractions in [[Astronomy:Comet|comet]]s and planets exposed to significant heat from the [[Astronomy:Sun|Sun]] over billions of years of [[Astronomy:Formation and evolution of the Solar System|solar system evolution]].

Deuterium is not radioactive, and does not represent a significant toxicity hazard. Water enriched in molecules that include deuterium instead of protium is called [[Chemistry:Heavy water|heavy water]]. Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for {{SimpleNuclide|Hydrogen|1}}-[[Physics:Nuclear magnetic resonance spectroscopy|nuclear magnetic resonance spectroscopy]]. Heavy water is used as a [[Physics:Neutron moderator|neutron moderator]] and coolant for nuclear reactors. Deuterium is also a potential fuel for commercial [[Physics:Nuclear fusion|nuclear fusion]].

== Hydrogen-3 (tritium) ==
{{Main|Physics:Tritium}}
[[File:H-3 atom.png|250px|thumbnail|right|A tritium atom contains one proton, two neutrons, and one electron.]]
'''{{SimpleNuclide|Hydrogen|3}}''' (atomic mass {{val|3.016049281320|(81)|ul=Da}}) is known as ''[[Physics:Tritium|tritium]]'' and contains one proton and two neutrons in its nucleus. It is radioactive, decaying into [[Physics:Helium-3|helium-3]] through [[Physics:Beta decay|β− decay]] with a [[Physics:Half-life|half-life]] of {{val|12.32|(2)|u=years}}.{{refn|group=nb|name=NUBASE2020 tropical year}}<ref name=NUBASE2020a/> Trace amounts of tritium occur naturally because of the interaction of cosmic rays with atmospheric gases. Tritium has also been released during nuclear weapons tests. It is used in thermonuclear fusion weapons, as a tracer in [[Chemistry:Isotope geochemistry|isotope geochemistry]], and specialized in [[Earth:Tritium radioluminescence|self-powered lighting]] devices.

The most common method of producing tritium is by bombarding a natural isotope of lithium, [[Physics:Isotopes of lithium#Lithium-6|lithium-6]], with neutrons in a [[Physics:Nuclear reactor|nuclear reactor]].

Tritium can be used in chemical and biological labeling experiments as a [[Biology:Radioactive tracer|radioactive tracer]].<ref name="BNT">{{cite web |author1=Pfizer Japan |website=Pharmaceuticals and Medical Devices Agency (Japan) |at=2.6.5.5B, pp. 6–8 |quote=[<sup>3</sup>H]-Labelled LNP-mRNA |title=SARS-CoV-2 mRNA Vaccine (BNT162, PF-07302048) |access-date=5 June 2021 |url=http://www.pmda.go.jp/drugs/2021/P20210212001/672212000_30300AMX00231_I100_1.pdf#page=16 |archive-date=24 March 2022|archive-url=https://web.archive.org/web/20220324171847/http://www.pmda.go.jp/drugs/2021/P20210212001/672212000_30300AMX00231_I100_1.pdf#page=16 }}</ref><ref name="green20">{{cite journal |doi=10.1093/jn/nxaa092|pmc=7330459 |journal=The Journal of Nutrition |title=Vitamin A Absorption Determined in Rats Using a Plasma Isotope Ratio Method |year=2020 |last1=Green |first1=Joanne Balmer |last2=Green |first2=Michael H. |volume=150 |issue=7 |pages=1977–1981 |pmid=32271921}}</ref> [[Physics:Deuterium–tritium fusion|D-T nuclear fusion]] uses tritium as its main reactant, along with [[Physics:Deuterium|deuterium]], liberating energy through the loss of mass when the two nuclei collide and fuse at high temperatures.

== Hydrogen-4 ==
'''{{SimpleNuclide|Hydrogen|4}}''' ([[Physics:Atomic mass|atomic mass]] {{val|4.02643|(11)}}) contains one proton and three neutrons in its nucleus. It is a highly [[Physics:Radionuclide|unstable]] isotope of hydrogen. It has been synthesized in the laboratory by bombarding [[Physics:Tritium|tritium]] with fast-moving [[Physics:Deuterium|deuterium]] nuclei.<ref name="Ter-Akopian">
{{cite journal
 |author=G. M. Ter-Akopian|year=2002
 |title=Hydrogen-4 and Hydrogen-5 from t+t and t+d transfer reactions studied with a 57.5-MeV triton beam
 |journal=AIP Conference Proceedings
 |volume=610 |pages=920–924
 |doi=10.1063/1.1470062
 |bibcode=2002AIPC..610..920T
 |display-authors=0}}</ref> In this experiment, the tritium nucleus captured a neutron from the fast-moving deuterium nucleus. The presence of the hydrogen-4 was deduced by detecting the emitted protons. It decays through [[Physics:Neutron emission|neutron emission]] into hydrogen-3 (tritium) with a [[Physics:Half-life|half-life]] of {{val|139|(10)|ul=ys}} (or {{val|1.39e-22|(10)|u=s}}).

In the 1955 satirical novel ''The Mouse That Roared'', the name ''quadium'' was given to the hydrogen-4 isotope that powered the ''Q-bomb'' that the Duchy of Grand Fenwick captured from the United States.

== Hydrogen-5 ==
'''{{SimpleNuclide|Hydrogen|5}}''' ([[Physics:Atomic mass|atomic mass]] {{val|5.03531|(10)}}) is a highly unstable isotope of hydrogen. The nucleus consists of a proton and four neutrons. It has been synthesized in the laboratory by bombarding tritium with fast-moving tritium nuclei.<ref name="Ter-Akopian" /><ref>
{{cite journal
 | author = A. A. Korsheninnikov| year = 2001
 | title = Superheavy Hydrogen <sup>5</sup>H
 | journal = [[Physics:Physical Review Letters|Physical Review Letters]]
 | volume = 87 | issue =  9| pages = 92501
 | bibcode=2001PhRvL..87i2501K
 | doi = 10.1103/PhysRevLett.87.092501
 | pmid=11531562
 |display-authors=0}}</ref> In this experiment, one tritium nucleus captures two neutrons from the other, becoming a nucleus with one proton and four neutrons. The remaining proton may be detected, and the existence of hydrogen-5 deduced. It decays through double [[Physics:Neutron emission|neutron emission]] into hydrogen-3 (tritium) and has a [[Physics:Half-life|half-life]] of {{val|86|(6)|ul=ys}} ({{val|8.6e-23|(6)|u=s}}) – the shortest half-life of any known nuclide.<ref name=NUBASE2020a/>

== Hydrogen-6 ==
'''{{SimpleNuclide|Hydrogen|6}}'''  ([[Physics:Atomic mass|atomic mass]] {{val|6.04496|(27)}}) consists of a [[Physics:Proton|proton]] and five [[Physics:Neutron|neutron]]s. It decays either through triple [[Physics:Neutron emission|neutron emission]] into hydrogen-3 (tritium) or quadruple neutron emission into hydrogen-2 (deuterium) and has a [[Physics:Half-life|half-life]] of {{val|294|(67)|ul=ys}} ({{val|2.94e-22|(67)|u=s}}).

== Hydrogen-7 ==
'''{{SimpleNuclide|Hydrogen|7}}''' ([[Physics:Atomic mass|atomic mass]] {{val|7.05275|(108)}}) consists of a [[Physics:Proton|proton]] and six [[Physics:Neutron|neutron]]s. It was first synthesized in 2003 by a group of Russian, Japanese and French scientists at [[Organization:Riken|RIKEN's]] [[Organization:Radioactive Isotope Beam Factory|Radioactive Isotope Beam Factory]] by bombarding [[Chemistry:Hydrogen|hydrogen]] with [[Physics:Isotopes of helium#Heavier helium isotopes|helium-8]] atoms. In the resulting reaction, all six of the helium-8 neutrons were donated to the hydrogen's nucleus. The two remaining protons were detected by the "RIKEN telescope", a device composed of several layers of sensors, positioned behind the target of the RI Beam cyclotron.<ref name="Korsheninnikov" /> Hydrogen-7 has a half-life of {{val|652|(558)|ul=ys}} ({{val|6.52e-22|(558)|u=s}}).<ref name=NUBASE2020a/>

==Decay chains==
The majority of heavy hydrogen isotopes decay directly to {{SimpleNuclide|Hydrogen|3}}, which then decays to the stable isotope {{SimpleNuclide|Helium|3|link=yes}}. However, {{SimpleNuclide|Hydrogen|6}} has occasionally been observed to decay directly to stable {{SimpleNuclide|Hydrogen|2}}.

:<math chem>\begin{array}{rcl}\\
\ce{^3_1H} &\ce{->[12.32\ \ce{y}]} &\ce{{^3_2He} + e^-} \\
\ce{^4_1H} &\ce{->[139\ \ce{ys}]} &\ce{{^3_1H} + {^1_0n}} \\
\ce{^5_1H} &\ce{->[86\ \ce{ys}]} &\ce{{^3_1H} + {2^1_0n}} \\
\ce{^6_1H} &\ce{->[294\ \ce{ys}]} &\ce{{^3_1H} + {3^1_0n}} \\
\ce{^6_1H} &\ce{->[294\ \ce{ys}]} &\ce{{^2_1H} + {4^1_0n}} \\
\ce{^7_1H} &\ce{->[652\ \ce{ys}]} &\ce{{^3_1H} + {4^1_0n}} \\{}
\end{array}</math>

Decay times are in [[Orders of magnitude (time)#Yoctosecond|yoctoseconds]] ({{val|e=-24|u=s}}) for all these isotopes except {{SimpleNuclide|Hydrogen|3}}, which is expressed in years.

==See also==
* [[Biology:Hydrogen isotope biogeochemistry|Hydrogen isotope biogeochemistry]]
* [[Physics:Exotic atom#Muonic helium (Hydrogen-4.1)|Hydrogen-4.1 (Muonic helium)]]
* [[Physics:Muonium|Muonium]] – acts like an exotic light isotope of hydrogen

==Notes==
{{reflist|group=nb}}

==References==
{{Reflist}}

==Further reading==
*{{cite web
 |first=B. |last=Dumé
 |date=7 March 2003
 |title=Hydrogen-7 makes its debut
 |url=http://physicsworld.com/cws/article/news/2003/mar/07/hydrogen-7-makes-its-debut
 |work=Physics World
 |url-access=registration 
}}

{{Navbox element isotopes}}


[[Category:Isotopes of hydrogen| ]]
[[Category:Hydrogen]]
[[Category:Lists of isotopes by element|Hydrogen]]

{{Sourceattribution|Isotopes of hydrogen}}