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Isotopes of carbon

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Isotopes ofcarbon (6C)
Main isotopes[1]Decay
Isotopeabun­dancehalf-life(t1/2)modepro­duct
11Csynth20.34 minβ+11B
12C98.9%stable
13C1.06%stable
14Ctrace5.70×103 yβ−14N
Standard atomic weightAr°(C)

Carbon (6C) has 14 knownisotopes, from8
C to20
C as well as22
C, of which only12
C and13
C arestable. The longest-livedradioisotope is14
C, with ahalf-life of 5700 years. This is also the only carbon radioisotope found in nature, as trace quantities are formedcosmogenically by the reaction14
N +n →14
C +1
H. The most stable artificial radioisotope is11
C, which has a half-life of20.34 min. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. Lighter isotopes exhibit beta-plus decay intoisotopes of boron and heavier ones beta-minus decay intoisotopes of nitrogen, though at the limits particle emission occurs as well.

List of isotopes

[edit]

Nuclide
ZNIsotopic mass(Da)[4]
[n 1]		Half-life[1]

[resonance width]		Decay
mode[1]
[n 2]		Daughter
isotope
[n 3]		Spin and
parity[1]
[n 4][n 5]		Natural abundance(mole fraction)
Normal proportion[1]Range of variation
8
C		628.037643(20)3.5(1.4) zs
[230(50) keV]		2p6
Be[n 6]		0+
9
C		639.0310372(23)126.5(9) msβ+ (54.1(1.7)%)9
B[n 7]		3/2−
β+α (38.4(1.6)%)5
Li[n 7]
β+p (7.5(6)%)8
Be[n 7]
10
C		6410.01685322(8)19.3011(15) sβ+10
B		0+
11
C[n 8]		6511.01143260(6)20.3402(53) minβ+11
B		3/2−
11m
C		12160(40) keVp?10
B ?		1/2+
12
C		6612 exactly[n 9]Stable0+[0.9884,0.9904][5]
13
C[n 10]		6713.003354835336(252)Stable1/2−[0.0096,0.0116][5]
14
C[n 11]		6814.003241989(4)5.70(3)×103 yβ−14
N		0+Trace[n 12]< 10−12
14m
C		22100(100) keVIT14
C		(2−)
15
C		6915.0105993(9)2.449(5) sβ−15
N		1/2+
16
C		61016.014701(4)750(6) msβ−n (99.0(3)%)15
N		0+
β− (1.0(3)%)16
N
17
C		61117.022579(19)193(6) msβ− (71.6(1.3)%)17
N		3/2+
β−n (28.4(1.3)%)16
N
β−2n ?15
N ?
18
C		61218.02675(3)92(2) msβ− (68.5(1.5)%)18
N		0+
β−n (31.5(1.5)%)17
N
β−2n ?16
N ?
19
C[n 13]		61319.03480(11)46.2(2.3) msβ−n (47(3)%)18
N		1/2+
β− (46.0(4.2)%)19
N
β−2n (7(3)%)17
N
20
C		61420.04026(25)16(3) msβ−n (70(11)%)19
N		0+
β−2n (<18.6%)18
N
β− (>11.4%)20
N
22
C[n 14]		61622.05755(25)6.2(1.3) msβ−n (61(14)%)21
N		0+
β−2n (<37%)20
N
β− (>2%)22
N
This table header & footer:
  1. ^( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  2. ^Modes of decay:
    EC:Electron capture



    n:Neutron emission
    p:Proton emission
  3. ^Bold symbol as daughter – Daughter product is stable.
  4. ^( ) spin value – Indicates spin with weak assignment arguments.
  5. ^# – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  6. ^Also immediately emits two protons for the net reaction of8
    C     →4
    He     +4 1
    H
  7. ^abcAll three product nuclei are unbound and so the net reaction in each case is9
    C     →2 4
    He     +1
    H     +e+
  8. ^Used for labeling molecules inPET scans
  9. ^Thedalton is defined as 1/12 of the mass of an unbound atom of carbon-12 in its ground state.
  10. ^Ratio of12C to13C used to measure biological productivity in ancient times and differing types ofphotosynthesis
  11. ^Has an important use inradiodating (seecarbon dating)
  12. ^Primarilycosmogenic, produced byneutrons striking atoms of14
    N     (14
    N     +n →14
    C     +1
    H    )
  13. ^Has 1halo neutron
  14. ^Has 2 halo neutrons

Carbon-11

[edit]

Carbon-11 or11
C is a radioactive isotope ofcarbon that decays toboron-11 with a half-life to 20.34 minutes. This decay mainly occurs due topositron emission, with around 0.19–0.23% of decays instead occurring byelectron capture.[6][7]

11
C →11
B +e+
 +ν
e +0.96 MeV
11
C +e−
 →11
B +ν
e +1.98 MeV

It is produced by hitting nitrogen withprotons of around 16.5MeV in acyclotron. The causes the endothermic reaction[8][9]

14
N +p →11
C +4
He − 2.92 MeV

It can also be produced by fragmentation of12
C by shooting high-energy12
C at a target.[10]

Carbon-11 is commonly used as aradioisotope for the radioactive labeling of molecules inpositron emission tomography. Among the many molecules used in this context are theradioligands[11
C]DASB and[11
C]Cimbi-5.

Natural isotopes

[edit]
Main articles:Carbon-12,Carbon-13, andCarbon-14

There are three naturally occurring isotopes of carbon: carbon-12, carbon-13, and carbon-14.12
C and13
C are stable, accounting for approximately 98.9% and 1.1% (respectively) of the naturally occurring carbon on Earth,[2] while14
C (also called radiocarbon) occurs in trace amounts and has a half-life of 5700 years. The primary source of14
C on Earth is the reaction of14
N with thermal neutrons from cosmic radiation in the upper atmosphere; this mixes throughout the atmosphere, and biological processes such as photosynthesis incorporate the14
C into living organisms. Since organisms stop absorbing14
C upon dying, measurement of the amount of14
C in a sample may be used to estimate its age. This technique is calledradiocarbon dating and is one of the principal methods ofradiometric dating in the field of archaeology.

Paleoclimate

[edit]

12
C and13
C are measured as theisotope ratioδ13C inbenthicforaminifera and used as aproxy fornutrient cycling and the temperature dependent air–sea exchange of CO2 (ventilation).[11] Plants find it easier to use the lighter isotope (12
C) when they convert sunlight and carbon dioxide into food. For example, large blooms ofplankton (free-floating organisms) absorb large amounts of12
C from the oceans. Originally, the12
C 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 away12
C from the surface, leaving the surface layers relatively rich in13
C. Where cold waters well up from the depths (such as in theNorth Atlantic), the water carries12
C back up with it; when the ocean was less stratified than today, there was much more12
C in the skeletons of surface-dwelling species. Other indicators of past climate include the presence of tropical species and coral growth rings.[12]

Tracing food sources and diets

[edit]

The quantities of the different isotopes can be measured bymass spectrometry and compared to astandard; the result (e.g., the delta of the13
C = δ13
C) is expressed as parts per thousand (‰ or "per mille") divergence from the ratio of a standard:[13]

δC13=((C13C12)sample(C13C12)standard−1)×1000{\displaystyle \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} ‰

The usual standard isPeedee Belemnite, abbreviated "PDB", a fossilbelemnite. Due to shortage of the original PDB sample, artificial "Vienna PDB", or "VPDB", is generally used today.[14]

Different photosynthetic pathways preferentially select for the lighter12
C, but their selectivity differs.[citation needed] Grasses intemperate climates (barley,rice,wheat,rye, andoats, plussunflower,potato,tomatoes,peanuts,cotton,sugar beet, and most trees and their nuts or fruits,roses, andKentucky bluegrass) follow aC3 photosynthetic pathway that will yield δ13C values averaging about −26.5‰.[citation needed] Grasses in hotarid climates (maize in particular, but alsomillet,sorghum,sugar cane, andcrabgrass) follow aC4 photosynthetic pathway that produces δ13C values averaging about −12.5‰.[15]

It follows that eating these different plants will affect the δ13C values in the consumer's body tissues. If an animal (or human) eats only C3 plants, their δ13C values will be from −18.5 to −22.0‰ in their bonecollagen and −14.5‰ in thehydroxylapatite of their teeth and bones.[16]

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

In case studies, millet and maize eaters can easily be distinguished from rice and wheat eaters.[citation needed] 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).[17]

See also

[edit]

Daughter products other than carbon

References

[edit]
  1. ^abcdeKondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021)."The NUBASE2020 evaluation of nuclear properties"(PDF).Chinese Physics C.45 (3) 030001.doi:10.1088/1674-1137/abddae.
  2. ^ab"Standard Atomic Weights: Carbon".CIAAW. 2009.
  3. ^Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04)."Standard atomic weights of the elements 2021 (IUPAC Technical Report)".Pure and Applied Chemistry.doi:10.1515/pac-2019-0603.ISSN 1365-3075.
  4. ^Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*".Chinese Physics C.45 (3) 030003.doi:10.1088/1674-1137/abddaf.
  5. ^ab"Atomic Weight of Carbon".CIAAW.
  6. ^Scobie, J.; Lewis, G. M. (1 September 1957). "K-capture in carbon 11".Philosophical Magazine.2 (21):1089–1099.Bibcode:1957PMag....2.1089S.doi:10.1080/14786435708242737.
  7. ^Campbell, J. L.; Leiper, W.; Ledingham, K. W. D.; Drever, R. W. P. (1967-04-11). "The ratio of K-capture to positron emission in the decay of11C".Nuclear Physics A.96 (2):279–287.Bibcode:1967NuPhA..96..279C.doi:10.1016/0375-9474(67)90712-9.
  8. ^"Carbon-11 Production and Transformation".Scholarly Community Encyclopedia.
  9. ^Lu, Shuiyu; et al. (Jan 18, 2024)."Gas Phase Transformations in Carbon-11 Chemistry".Int. J. Mol. Sci.25 (2): 1167.doi:10.3390/ijms25021167.PMC 10816134.PMID 38256240.
  10. ^Daria Boscolo; et al. (2025). "Image-guided treatment of mouse tumours with radioactive ion beams".Nature Physics.21 (10):1648–1656.arXiv:2409.14898.doi:10.1038/s41567-025-02993-8.
  11. ^Lynch-Stieglitz, Jean; Stocker, Thomas F.; Broecker, Wallace S.; Fairbanks, Richard G. (1995)."The influence of air-sea exchange on the isotopic composition of oceanic carbon: Observations and modeling".Global Biogeochemical Cycles.9 (4):653–665.Bibcode:1995GBioC...9..653L.doi:10.1029/95GB02574.S2CID 129194624.
  12. ^Tim FlanneryThe weather makers: the history & future of climate change, The Text Publishing Company, Melbourne, Australia.ISBN 1-920885-84-6
  13. ^Miller, Charles B.; Wheeler, Patricia (2012).Biological oceanography (2nd ed.). Chichester, West Sussex: John Wiley & Sons, Ltd. p. 186.ISBN 9781444333022.OCLC 794619582.
  14. ^Faure, Gunter; Mensing, Teresa M. (2005). "27 Carbon".Isotopes: Principles and Applications (Third ed.). Hoboken, NJ: Wiley.ISBN 978-81-265-3837-9.
  15. ^O'Leary, Marion H. (May 1988)."Carbon Isotopes in Photosynthesis"(PDF).BioScience.38 (5):328–336.doi:10.2307/1310735.JSTOR 1310735.S2CID 29110460. Retrieved17 November 2022.
  16. ^Tycot, R. H. (2004). M. Martini; M. Milazzo; M. Piacentini (eds.)."Stable isotopes and diet: you are what you eat"(PDF).Proceedings of the International School of Physics "Enrico Fermi" Course CLIV.
  17. ^Richard, Hedges (2006)."Where does our protein come from?".British Journal of Nutrition.95 (6):1031–1032.doi:10.1079/bjn20061782.PMID 16768822.
Group12 3456789101112131415161718
PeriodHydrogen and
alkali metals		Alkaline
earth metals		Pnicto­gensChal­co­gensHalo­gensNoble gases
①12
②345678910
③1112131415161718
④192021222324252627282930313233343536
⑤373839404142434445464748495051525354
⑥55561 asterisk71727374757677787980818283848586
⑦87881 asterisk103104105106107108109110111112113114115116117118
⑧119120
1 asterisk5758596061626364656667686970 
1 asterisk8990919293949596979899100101102
National
Other
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