View source for Physics:Isotopes of carbon

{{Short description|Carbon with different numbers of neutrons}}
{{Infobox carbon isotopes}}
[[Chemistry:Carbon|Carbon]] (<sub>6</sub>C) has 15 known [[Physics:Isotope|isotope]]s, from {{SimpleNuclide|Carbon|8}} to {{SimpleNuclide|Carbon|22}}, of which {{SimpleNuclide|Carbon|12|link=yes}} and {{SimpleNuclide|Carbon|13|link=yes}} are [[Physics:Stable nuclide|stable]]. The longest-lived [[Physics:Radionuclide|radioisotope]] is {{SimpleNuclide|Carbon|14|link=yes}}, with a [[Physics:Half-life|half-life]] of {{val|5.70|(3)|e=3}} years. This is also the only carbon radioisotope found in nature, as trace quantities are formed [[Physics:Cosmogenic nuclide|cosmogenically]] by the reaction {{SimpleNuclide|Nitrogen|14}} + {{Subatomic particle|neutron}} → {{SimpleNuclide|Carbon|14}} + {{SimpleNuclide|Hydrogen|1}}. The most stable artificial radioisotope is {{SimpleNuclide|Carbon|11}}, which has a half-life of {{val|20.3402|(53)|u=min}}. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. The least stable isotope is {{SimpleNuclide|Carbon|8}}, with a half-life of {{val|3.5|(1.4)|e=-21|u=s}}. Light isotopes tend to decay into [[Physics:Isotopes of boron|isotopes of boron]] and heavy ones tend to decay into [[Physics:Isotopes of nitrogen|isotopes of nitrogen]].

==List of isotopes==
{{Isotopes table
|symbol=C
|refs=NUBASE2020, AME2020 II
|notes=mass#, unc(), var[], spin(), spin#, resonance, daughter-st, EC, n, p
}}
|-
| {{SimpleNuclide|Carbon|8}}
| style="text-align:right" | 6
| style="text-align:right" | 2
| {{val|8.037643|(20)}}
| {{val|3.5|(1.4)|u=zs}}<br>[{{val|230|(50)|u=keV}}]
| [[Physics:Proton emission|2p]]
| {{SimpleNuclide|Beryllium|6}}<ref group="n">Subsequently decays by double proton emission to '''{{SimpleNuclide|Helium|4}}''' for a net reaction of {{SimpleNuclide|Carbon|8}} → '''{{SimpleNuclide|Helium|4}}''' + 4'''{{SimpleNuclide|Hydrogen|1}}'''</ref>
| 0+
|
|
|-
| rowspan=3|{{SimpleNuclide|Carbon|9}}
| rowspan=3 style="text-align:right" | 6
| rowspan=3 style="text-align:right" | 3
| rowspan=3|{{val|9.0310372|(23)}}
| rowspan=3|{{val|126.5|(9)|u=ms}}
| β<sup>+</sup> ({{val|54.1|(1.7)|u=%}})
| {{SimpleNuclide|Boron|9}}
| rowspan=3|3/2−
| rowspan=3|
| rowspan=3|
|-
| β<sup>+</sup>α ({{val|38.4|(1.6)|u=%}})
| {{SimpleNuclide|Lithium|5}}<ref group="n">Immediately decays by proton emission to '''{{SimpleNuclide|Helium|4}}''' for a net reaction of {{SimpleNuclide|Carbon|9}} → 2&nbsp;'''{{SimpleNuclide|Helium|4}}''' + '''{{SimpleNuclide|Hydrogen|1}}''' + {{Subatomic particle|electron}}</ref>
|-
| β<sup>+</sup>p ({{val|7.5|(6)|u=%}})
| {{SimpleNuclide|Beryllium|8}}<ref group="n">Immediately decays into two '''{{SimpleNuclide|Helium|4}}''' atoms for a net reaction of {{SimpleNuclide|Carbon|9}} → 2&nbsp;'''{{SimpleNuclide|Helium|4}}''' + '''{{SimpleNuclide|Hydrogen|1}}''' + {{Subatomic particle|electron}}</ref>
|-
| {{SimpleNuclide|Carbon|10}}
| style="text-align:right" | 6
| style="text-align:right" | 4
| {{val|10.01685322|(8)}}
| {{val|19.3011|(15)|u=s}}
| β<sup>+</sup>
| '''{{SimpleNuclide|Boron|10}}'''
| 0+
|
|
|-
| rowspan=1|{{SimpleNuclide|Carbon|11}}<ref group="n">Used for labeling molecules in [[Physics:Positron emission tomography|PET scans]]</ref>
| rowspan=1 style="text-align:right" | 6
| rowspan=1 style="text-align:right" | 5
| rowspan=1 |{{val|11.01143260|(6)}}
| rowspan=1 |{{val|20.3402|(53)|u=min}}
| β<sup>+</sup>
| '''{{SimpleNuclide|Boron|11}}'''
| rowspan=1 |3/2−
| rowspan=1 |
| rowspan=1 |
|-
| style="text-indent:1em" |{{SimpleNuclide|Carbon|11m}}
| colspan=3 style="text-indent:2em" |{{val|12160|(40)|u=keV}}
|
| p ?<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|Boron|10}}''' ?
| 1/2+
|
|
|-
| {{SimpleNuclide|Carbon|12|link=yes}}
| style="text-align:right" | 6
| style="text-align:right" | 6
| 12 exactly<ref group="n">The [[Physics:Unified atomic mass unit|unified atomic mass unit]] is defined as 1/12 of the mass of an unbound atom of carbon-12 in its ground state.</ref>
| colspan=3 align=center|'''Stable'''
| 0+
| [{{val|0.9884}}, {{val|0.9904}}]<ref name="Atomic Weight of Carbon">{{cite web |title=Atomic Weight of Carbon |url=https://ciaaw.org/carbon.htm |website=CIAAW}}</ref>
|-
| {{SimpleNuclide|Carbon|13|link=yes}}<ref group="n">[[Biology:Δ13C|Ratio of <sup>12</sup>C to <sup>13</sup>C]] used to measure biological productivity in ancient times and differing types of [[Earth:Photosynthesis|photosynthesis]]</ref>
| style="text-align:right" | 6
| style="text-align:right" | 7
| {{val|13.003354835336|(252)}}
| colspan=3 align=center|'''Stable'''
| 1/2−
| [{{val|0.0096}}, {{val|0.0116}}]<ref name="Atomic Weight of Carbon"/>
|-
| {{SimpleNuclide|Carbon|14|link=yes}}<ref group="n">Has an important use in radiodating (see carbon dating)</ref>
| style="text-align:right" | 6
| style="text-align:right" | 8
| {{val|14.003241989|(4)}}
| {{val|5.70|(3)|e=3|u=y}}
| β<sup>−</sup>
| '''{{SimpleNuclide|Nitrogen|14}}'''
| 0+
| Trace<ref group="n">Primarily cosmogenic, produced by [[Physics:Neutron|neutron]]s striking atoms of {{SimpleNuclide|Nitrogen|14|link=yes}} ({{SimpleNuclide|Nitrogen|14}} + {{Subatomic particle|neutron}} → {{SimpleNuclide|Carbon|14}} + {{SimpleNuclide|Hydrogen|1}})</ref>
| < 10<sup>−12</sup>
|-
| style="text-indent:1em" |{{SimpleNuclide|Carbon|14m}}
| colspan="3" style="text-indent:2em" |{{val|22100|(100)|u=keV}}
|
| IT
| {{SimpleNuclide|Carbon|14}}
| (2−)
|
|
|-
| {{SimpleNuclide|Carbon|15}}
| style="text-align:right" | 6
| style="text-align:right" | 9
| {{val|15.0105993|(9)}}
| {{val|2.449|(5)|u=s}}
| β<sup>−</sup>
| '''{{SimpleNuclide|Nitrogen|15}}'''
| 1/2+
|
|
|-
| rowspan=2|{{SimpleNuclide|Carbon|16}}
| rowspan=2 style="text-align:right" | 6
| rowspan=2 style="text-align:right" | 10
| rowspan=2|{{val|16.014701|(4)}}
| rowspan=2|{{val|750|(6)|u=ms}}
| β<sup>−</sup>[[Physics:Neutron emission|n]] ({{val|99.0|(3)|u=%}})
| '''{{SimpleNuclide|Nitrogen|15}}'''
| rowspan=2|0+
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup> ({{val|1.0|(3)|u=%}})
| {{SimpleNuclide|Nitrogen|16}}
|-
| rowspan=3|{{SimpleNuclide|Carbon|17}}
| rowspan=3 style="text-align:right" | 6
| rowspan=3 style="text-align:right" | 11
| rowspan=3|{{val|17.022579|(19)}}
| rowspan=3|{{val|193|(6)|u=ms}}
| β<sup>−</sup> ({{val|71.6|(1.3)|u=%}})
| {{SimpleNuclide|Nitrogen|17}}
| rowspan=3|3/2+
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup>n ({{val|28.4|(1.3)|u=%}})
| {{SimpleNuclide|Nitrogen|16}}
|-
| β<sup>−</sup>2n ?<ref group="n" name="decay mode 1"/>
| '''{{SimpleNuclide|Nitrogen|15}}''' ?
|-
| rowspan=3|{{SimpleNuclide|Carbon|18}}
| rowspan=3 style="text-align:right" | 6
| rowspan=3 style="text-align:right" | 12
| rowspan=3|{{val|18.02675|(3)}}
| rowspan=3|{{val|92|(2)|u=ms}}
| β<sup>−</sup> ({{val|68.5|(1.5)|u=%}})
| {{SimpleNuclide|Nitrogen|18}}
| rowspan=3|0+
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup>n ({{val|31.5|(1.5)|u=%}})
| {{SimpleNuclide|Nitrogen|17}}
|-
| β<sup>−</sup>2n ?<ref group="n" name="decay mode 1"/>
| {{SimpleNuclide|Nitrogen|16}} ?
|-
| rowspan=3|{{SimpleNuclide|Carbon|19}}<ref group="n">Has 1 [[Physics:Halo nucleus|halo]] neutron</ref>
| rowspan=3 style="text-align:right" | 6
| rowspan=3 style="text-align:right" | 13
| rowspan=3|{{val|19.03480|(11)}}
| rowspan=3|{{val|46.2|(2.3)|u=ms}}
| β<sup>−</sup>n ({{val|47|(3)|u=%}})
| {{SimpleNuclide|Nitrogen|18}}
| rowspan=3|1/2+
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup> ({{val|46.0|(4.2)|u=%}})
| {{SimpleNuclide|Nitrogen|19}}
|-
| β<sup>−</sup>2n ({{val|7|(3)|u=%}})
| {{SimpleNuclide|Nitrogen|17}}
|-
| rowspan=3|{{SimpleNuclide|Carbon|20}}
| rowspan=3 style="text-align:right" | 6
| rowspan=3 style="text-align:right" | 14
| rowspan=3|{{val|20.04026|(25)}}
| rowspan=3|{{val|16|(3)|u=ms}}
| β<sup>−</sup>n ({{val|70|(11)|u=%}})
| {{SimpleNuclide|Nitrogen|19}}
| rowspan=3|0+
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup>2n (< {{val|18.6|u=%}})
| {{SimpleNuclide|Nitrogen|18}}
|-
| β<sup>−</sup> (> {{val|11.4|u=%}})
| {{SimpleNuclide|Nitrogen|20}}
|-
| {{SimpleNuclide|Carbon|21}}?<ref group="n" name="unconfirmed">This isotope has not yet been observed; given data is inferred or estimated from periodic trends.</ref>
| style="text-align:right" | 6
| style="text-align:right" | 15
| {{val|21.04900|(64)}}#
| < {{val|30|u=ns}}
| n ?<ref group="n" name="decay mode 1"/>
| {{SimpleNuclide|Carbon|20}} ?
| 1/2+#
|
|
|-
| rowspan=3|{{SimpleNuclide|Carbon|22}}<ref group="n">Has 2 halo neutrons</ref>
| rowspan=3 style="text-align:right" | 6
| rowspan=3 style="text-align:right" | 16
| rowspan=3|{{val|22.05755|(25)}}
| rowspan=3|{{val|6.2|(1.3)|u=ms}}
| β<sup>−</sup>n ({{val|61|(14)|u=%}})
| {{SimpleNuclide|Nitrogen|21}}
| rowspan=3|0+
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup>2n (< {{val|37|u=%}})
| {{SimpleNuclide|Nitrogen|20}}
|-
| β<sup>−</sup> (> {{val|2|u=%}})
| {{SimpleNuclide|Nitrogen|22}}
|-
| {{SimpleNuclide|Carbon|23}}?<ref group="n" name="unconfirmed"/>
| style="text-align:right" | 6
| style="text-align:right" | 17
| {{val|23.06889|(107)}}#
| 
| n ?<ref group="n" name="decay mode 1"/>
| {{SimpleNuclide|Carbon|22}}?
| 3/2+#
| 
| 

{{Isotopes table/footer}}

==Carbon-11==
'''Carbon-11''' or '''{{SimpleNuclide|Carbon|11}}''' is a radioactive isotope of [[Chemistry:Carbon|carbon]] that decays to [[Physics:Boron-11|boron-11]]. This decay mainly occurs due to [[Physics:Positron emission|positron emission]], with around 0.19–0.23% of decays instead occurring by [[Physics:Electron capture|electron capture]].<ref name="11C-Scobie">{{cite journal |last1=Scobie |first1=J. |last2=Lewis |first2=G. M. |title=K-capture in carbon 11 |journal=Philosophical Magazine |date=1 September 1957 |volume=2 |issue=21 |pages=1089–1099 |doi=10.1080/14786435708242737 |bibcode=1957PMag....2.1089S}}</ref><ref name="11C-Campbell">{{cite journal |last1=Campbell |first1=J. L. |last2=Leiper |first2=W. |last3=Ledingham |first3=K. W. D. |last4=Drever |first4=R. W. P. |title=The ratio of K-capture to positron emission in the decay of <sup>11</sup>C |journal=Nuclear Physics A |volume=96 |issue=2 |pages=279–287 |doi=10.1016/0375-9474(67)90712-9 |bibcode=1967NuPhA..96..279C |date=1967-04-11}}</ref> It has a [[Physics:Half-life|half-life]] of {{val|20.3402|(53)|u=minutes}}.

:{{SimpleNuclide|Carbon|11}} → {{SimpleNuclide|link=yes|Boron|11}} + {{SubatomicParticle|link=yes|positron}} + {{SubatomicParticle|link=yes|Electron neutrino}} + {{Val|0.96|ul=MeV}}
:{{SimpleNuclide|Carbon|11}} + {{SubatomicParticle|link=yes|Electron}} → {{SimpleNuclide|link=|Boron|11}} + {{SubatomicParticle|link=|Electron neutrino}} + {{Val|1.98|u=MeV}}

It is produced from nitrogen in a [[Physics:Cyclotron|cyclotron]] by the reaction
:{{SimpleNuclide|Nitrogen|14}} + {{SubatomicParticle|link=yes|proton}} → {{SimpleNuclide|Carbon|11}} + {{SimpleNuclide|Helium|4}}

Carbon-11 is commonly used as a radioisotope for the radioactive labeling of molecules in [[Physics:Positron emission tomography|positron emission tomography]]. Among the many molecules used in this context are the [[Biology:Radioligand|radioligand]]s [[Chemistry:DASB|[{{SimpleNuclide|Carbon|11}}]DASB]] and [[Chemistry:25I-NBOMe|[{{SimpleNuclide|Carbon|11}}]Cimbi-5]].

==Natural isotopes==
{{Main|Physics:Carbon-12|Physics:Carbon-13|Physics:Carbon-14}}
There are three naturally occurring [[Physics:Isotope|isotope]]s of carbon: 12, 13, and 14. {{SimpleNuclide|Carbon|12}} and {{SimpleNuclide|Carbon|13}} are stable, occurring in [[Biology:Δ13C|a natural proportion of approximately 93:1]]. {{SimpleNuclide|Carbon|14}} is produced by thermal neutrons from cosmic radiation in the upper atmosphere, and is transported down to earth to be absorbed by living biological material. Isotopically, {{SimpleNuclide|Carbon|14}} constitutes a negligible part; but, since it is radioactive with a half-life of {{val|5.70|(3)|e=3}} years, it is radiometrically detectable. Since dead tissue does not absorb {{SimpleNuclide|Carbon|14}}, the amount of {{SimpleNuclide|Carbon|14}} is one of the methods used within the field of archeology for [[Physics:Radiometric dating|radiometric dating]] of biological material.

==Paleoclimate==

{{SimpleNuclide|Carbon|12}} and {{SimpleNuclide|Carbon|13}} are measured as the [[Physics:Isotope analysis#Stable isotope analysis in aquatic ecosystems|isotope ratio]] [[Biology:Δ13C|δ<sup>13</sup>C]] in benthic [[Biology:Foraminifera|foraminifera]] and used as a [[Earth:Proxy (climate)|proxy]] for nutrient cycling and the temperature dependent air–sea exchange of CO<sub>2</sub> (ventilation).<ref>{{cite journal |last1=Lynch-Stieglitz |first1=Jean |last2=Stocker |first2=Thomas F. |last3=Broecker |first3=Wallace S. |last4=Fairbanks |first4=Richard G. |title=The influence of air-sea exchange on the isotopic composition of oceanic carbon: Observations and modeling |journal=Global Biogeochemical Cycles |date=1995 |volume=9 |issue=4 |pages=653–665 |doi=10.1029/95GB02574 |bibcode=1995GBioC...9..653L |s2cid=129194624 |url=https://boris.unibe.ch/158803/}}</ref> Plants find it easier to use the lighter isotopes ({{SimpleNuclide|Carbon|12}}) when they convert sunlight and carbon dioxide into food. So, for example, large blooms of [[Earth:Plankton|plankton]] (free-floating organisms) absorb large amounts of {{SimpleNuclide|Carbon|12}} from the oceans. Originally, the {{SimpleNuclide|Carbon|12}} was mostly incorporated into the seawater from the atmosphere. If the oceans that the plankton live in are stratified (meaning that there are layers of warm water near the top, and colder water deeper down), then the surface water does not mix very much with the deeper waters, so that when the plankton dies, it sinks and takes away {{SimpleNuclide|Carbon|12}} from the surface, leaving the surface layers relatively rich in {{SimpleNuclide|Carbon|13}}. Where cold waters well up from the depths (such as in the North Atlantic), the water carries {{SimpleNuclide|Carbon|12}} back up with it. So, when the ocean was less stratified than today, there was much more {{SimpleNuclide|Carbon|12}} in the skeletons of surface-dwelling species. Other indicators of past climate include the presence of tropical species, coral growths rings, etc.<ref name="C-Flannery">[[Biography:Tim Flannery|Tim Flannery]] ''The weather makers: the history & future of climate change'', The Text Publishing Company, Melbourne, Australia. {{ISBN|1-920885-84-6}}</ref>

==Tracing food sources and diets==
The quantities of the different isotopes can be measured by [[Physics:Mass spectrometry|mass spectrometry]] and compared to a standard; the result (e.g. the delta of the {{SimpleNuclide|Carbon|13}} = δ{{SimpleNuclide|Carbon|13}}) is expressed as parts per thousand (‰):<ref name="C-Miller">{{Cite book |title=Biological oceanography |last1=Miller |first1=Charles B. |publisher=John Wiley & Sons, Ltd. |last2=Wheeler |first2=Patricia |year=2012 |isbn=9781444333022 |edition=2nd |location=Chichester, West Sussex |page=186 |oclc=794619582}}</ref>
:<math chem>\delta \ce{^{13}C} = \left( \frac{\left( \frac\ce{^{13}C}\ce{^{12}C} \right)_\text{sample}}{\left( \frac\ce{^{13}C}\ce{^{12}C} \right)_\text{standard}} - 1 \right) \times 1000</math> ‰<!-- this must be \permil, but it does not work -->

Stable carbon isotopes in [[Chemistry:Carbon dioxide|carbon dioxide]] are utilized differentially by plants during [[Earth:Photosynthesis|photosynthesis]].{{Citation needed|reason=need provide a reference source|date=March 2017}} Grasses in [[Earth:Temperate climate|temperate climate]]s ([[Biology:Barley|barley]], [[Biology:Rice|rice]], [[Biology:Wheat|wheat]], [[Biology:Rye|rye]], and oats, plus sunflower, [[Biology:Potato|potato]], [[Biology:Tomato|tomato]]es, [[Biology:Peanut|peanut]]s, [[Biology:Cotton|cotton]], [[Biology:Sugar beet|sugar beet]], and most trees and their nuts or fruits, [[Biology:Rose|rose]]s, and Kentucky bluegrass) follow a [[Biology:C3 carbon fixation|C3 photosynthetic pathway]] that will yield δ<sup>13</sup>C values averaging about −26.5‰.{{Citation needed|reason=need to provide a reference|date=March 2017}} Grasses in hot arid climates ([[Biology:Maize|maize]] in particular, but also [[Biology:Millet|millet]], [[Biology:Sorghum|sorghum]], sugar cane, and crabgrass) follow a [[Biology:C4 carbon fixation|C4 photosynthetic pathway]] that produces δ<sup>13</sup>C values averaging about −12.5‰.<ref name="Oleary98">{{cite journal |last1=O'Leary |first1=Marion H. |title=Carbon Isotopes in Photosynthesis |journal=BioScience |date=May 1988 |volume=38 |issue=5 |pages=328–336 |doi=10.2307/1310735 |jstor=1310735 |s2cid=29110460 |url=https://www.ldeo.columbia.edu/~polissar/OrgGeochem/oleary-1988-carbon-isotopes.pdf |access-date=17 November 2022 |language=en}}</ref>

It follows that eating these different plants will affect the δ<sup>13</sup>C values in the consumer's body tissues. If an animal (or human) eats only C3 plants, their δ<sup>13</sup>C values will be from −18.5 to −22.0‰ in their bone [[Biology:Collagen|collagen]] and −14.5‰ in the hydroxylapatite of their teeth and bones.<ref name="C-Tycot">{{cite journal |last=Tycot |first=R. H. |year=2004 |title=Stable isotopes and diet: you are what you eat |journal=Proceedings of the International School of Physics "Enrico Fermi" Course CLIV |editor1=M. Martini |editor2=M. Milazzo |editor3=M. Piacentini |url=http://luna.cas.usf.edu/~rtykot/PR39%20-%20Enrico%20Fermi%20isotopes.pdf}}</ref>

In contrast, C4 feeders will have bone collagen with a value of −7.5‰ and hydroxylapatite value of −0.5‰.

In actual case studies, millet and maize eaters can easily be distinguished from rice and wheat eaters. Studying how these dietary preferences are distributed geographically through time can illuminate migration paths of people and dispersal paths of different agricultural crops. However, human groups have often mixed C3 and C4 plants (northern Chinese historically subsisted on wheat and millet), or mixed plant and animal groups together (for example, southeastern Chinese subsisting on rice and fish).<ref name="C-Richard">{{cite journal |first1= Hedges |last1=Richard |year=2006 |title=Where does our protein come from? |journal=British Journal of Nutrition |volume=95 |issue=6 |pages=1031–2 |doi=10.1079/bjn20061782 |pmid=16768822 |doi-access=free}}</ref>

==See also==
* Cosmogenic isotopes
* [[Physics:Environmental isotopes|Environmental isotopes]]
* [[Physics:Isotopic signature|Isotopic signature]]
* [[Physics:Radiocarbon dating|Radiocarbon dating]]

==References==
{{Reflist}}

{{Navbox element isotopes}}

[[Category:Isotopes of carbon| ]]
[[Category:Carbon]]
[[Category:Lists of isotopes by element|Carbon]]

{{Sourceattribution|Isotopes of carbon}}