Isotopes of carbon

Main isotopes of Chemistry:carbon (6C) | Iso­tope | Decay

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| abun­dance | half-life (t1/2) | mode | pro­duct
11C | syn | 20 min  | β+ | 11B
12C | 98.9%  | stable
13C | 1.1%  | stable
14C | 1 ppt | 5730 y  | β− | 14N
Standard atomic weight Ar, standard(C)|

* [12.0096, 12.0116][1]
* Conventional: 12.011

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Carbon (6C) has 14 known isotopes, from The element Chemistry:Carbon does not exist. to The element Chemistry:Carbon does not exist. as well as The element Chemistry:Carbon does not exist., of which only The element Chemistry:Carbon does not exist. and The element Chemistry:Carbon does not exist. are stable. The longest-lived radioisotope is The element Chemistry:Carbon does not exist., with a half-life of 5700 years. This is also the only carbon radioisotope found in nature, as trace quantities are formed cosmogenically by the reaction The element Chemistry:Nitrogen does not exist. \+ n → The element Chemistry:Carbon does not exist. \+ The element Chemistry:Hydrogen does not exist.. The most stable artificial radioisotope is The element Chemistry:Carbon does not exist., which has a half-life of 20.34 minutes. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. Lighter isotopes exhibit beta-plus decay into isotopes of boron and heavier ones beta-minus decay into isotopes of nitrogen, though at the limits particle emission occurs as well. The two lightest isotopes decay into helium via short-lived isotopes of lithium, beryllium and boron.

## Contents

* 1 List of isotopes
* 2 Carbon-11
* 3 Stable isotopes
* 3.1 Paleoclimate
* 3.2 Tracing food sources and diets
* 4 Carbon-14
* 5 See also
* 6 References

## List of isotopes

Nuclide
| Z | N | Isotopic mass (u)
[n 1] | Half-life

[resonance width]  | Decay
mode
[n 2] | Daughter
isotope
[n 3] | Spin and
parity
[n 4][n 5] | Physics:Natural abundance (mole fraction)

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Normal proportion  | Range of variation
The element Chemistry:Carbon does not exist. | 6  | 2  | 8.037643(20) | 1974 | 3.5(1.4) zs
[230(50) keV]  | 2p | The element Chemistry:Beryllium does not exist.[n 6] | 0+  |  |
The element Chemistry:Carbon does not exist. | 6  | 3  | 9.0310372(23) | 1964 | 126.5(9) ms | β+ (54.1(1.7)%)  | The element Chemistry:Boron does not exist.[n 7] | 3/2−  |  |
β+α (38.4(1.6)%)  | The element Chemistry:Lithium does not exist.[n 7]
β+p (7.5(6)%)  | The element Chemistry:Beryllium does not exist.[n 7]
The element Chemistry:Carbon does not exist. | 6  | 4  | 10.01685322(8) | 1949 | 19.3011(15) s | β+ | The element Chemistry:Boron does not exist. | 0+  |  |
The element Chemistry:Carbon does not exist.[n 8] | 6  | 5  | 11.01143260(6) | 1934 | 20.3402(53) min | β+ | The element Chemistry:Boron does not exist. | 3/2−  |
The element Chemistry:Carbon does not exist. | 6  | 6  | 12 exactly[n 9] | 1919 | Stable | 0+  | [0.9884, 0.9904][2]
The element Chemistry:Carbon does not exist.[n 10] | 6  | 7  | 13.003354835336(252) | 1929 | Stable | 1/2−  | [0.0096, 0.0116][2]
The element Chemistry:Carbon does not exist.[n 11] | 6  | 8  | 14.003241989(4) | 1936 | 5.70(3)×103 y | β− | The element Chemistry:Nitrogen does not exist. | 0+  | Trace[n 12]
The element Chemistry:Carbon does not exist. | 6  | 9  | 15.0105993(9) | 1950 | 2.449(5) s | β− | The element Chemistry:Nitrogen does not exist. | 1/2+  |  |
The element Chemistry:Carbon does not exist. | 6  | 10  | 16.014701(4) | 1961 | 750(6) ms | β−n (99.0(3)%)  | The element Chemistry:Nitrogen does not exist. | 0+  |  |
β− (1.0(3)%)  | The element Chemistry:Nitrogen does not exist.
The element Chemistry:Carbon does not exist. | 6  | 11  | 17.022579(19) | 1968 | 193(6) ms | β− (71.6(1.3)%)  | The element Chemistry:Nitrogen does not exist. | 3/2+  |  |
β−n (28.4(1.3)%)  | The element Chemistry:Nitrogen does not exist.
β−2n ?  | The element Chemistry:Nitrogen does not exist. ?
The element Chemistry:Carbon does not exist. | 6  | 12  | 18.02675(3) | 1969 | 92(2) ms | β− (68.5(1.5)%)  | The element Chemistry:Nitrogen does not exist. | 0+  |  |
β−n (31.5(1.5)%)  | The element Chemistry:Nitrogen does not exist.
β−2n ?  | The element Chemistry:Nitrogen does not exist. ?
The element Chemistry:Carbon does not exist.[n 13] | 6  | 13  | 19.03480(11) | 1974 | 46.2(2.3) ms | β−n (47(3)%)  | The element Chemistry:Nitrogen does not exist. | 1/2+  |  |
β− (46.0(4.2)%)  | The element Chemistry:Nitrogen does not exist.
β−2n (7(3)%)  | The element Chemistry:Nitrogen does not exist.
The element Chemistry:Carbon does not exist. | 6  | 14  | 20.04026(25) | 1981 | 16(3) ms | β−n (70(11)%)  | The element Chemistry:Nitrogen does not exist. | 0+  |  |
β−2n (< 18.6%)  | The element Chemistry:Nitrogen does not exist.
β− (> 11.4%)  | The element Chemistry:Nitrogen does not exist.
The element Chemistry:Carbon does not exist. | 6  | 15  | 21.04900(64)#  | (2015) | < 30 ns | n ?  | The element Chemistry:Carbon does not exist. ?  | 1/2+#  |  |
The element Chemistry:Carbon does not exist.[n 14] | 6  | 16  | 22.05755(25) | 1986 | 6.2(1.3) ms | β−n (61(14)%)  | The element Chemistry:Nitrogen does not exist. | 0+  |  |
β−2n (< 37%)  | The element Chemistry:Nitrogen does not exist.
β− (> 2%)  | The element Chemistry:Nitrogen does not exist.

1. ↑ ( ) - Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
2. ↑ Modes of decay:  EC: | Electron capture

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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 of The element Chemistry:Carbon does not exist. → The element Chemistry:Helium does not exist. \+ 4 The element Chemistry:Hydrogen does not exist.
7. ↑ 7.0 7.1 7.2 All three product nuclei are unbound and so the net reaction in each case is The element Chemistry:Carbon does not exist. → 2 The element Chemistry:Helium does not exist. \+ The element Chemistry:Hydrogen does not exist. \+ e+
8. ↑ Used for labeling molecules in PET scans
9. ↑ The dalton is defined as 1/12 of the mass of an unbound atom of carbon-12 in its ground state.
10. ↑ Ratio of 12C to 13C used to measure biological productivity in ancient times and differing types of photosynthesis
11. ↑ Has an important use in radiodating (see carbon dating)
12. ↑ Primarily cosmogenic, produced by neutrons striking atoms of The element Chemistry:Nitrogen does not exist. (The element Chemistry:Nitrogen does not exist. \+ n → The element Chemistry:Carbon does not exist. \+ The element Chemistry:Hydrogen does not exist.), <10−12
13. ↑ Has 1 halo neutron
14. ↑ Has 2 halo neutrons

## Carbon-11

Carbon-11 or The element Chemistry:Carbon does not exist. is a radioactive isotope of carbon that decays to boron-11 with a half-life to 20.34 minutes. This decay mainly occurs due to positron emission, with around 0.19–0.23% of decays instead occurring by electron capture.[3][4]

The element Chemistry:Carbon does not exist. → The element Chemistry:Boron does not exist. \+ positron + Electron neutrino + 0.96 MeV
The element Chemistry:Carbon does not exist. \+ e− → The element Chemistry:Boron does not exist. \+ νe \+ 1.98 MeV

It is produced by hitting nitrogen with protons of around 16.5 MeV in a cyclotron. The causes the endothermic reaction[5][6]

The element Chemistry:Nitrogen does not exist. \+ proton → The element Chemistry:Carbon does not exist. \+ The element Chemistry:Helium does not exist. − 2.92 MeV

It can also be produced by fragmentation of The element Chemistry:Carbon does not exist. by shooting high-energy The element Chemistry:Carbon does not exist. at a target.[7]

Carbon-11 is commonly used as a radioisotope for the radioactive labeling of molecules in positron emission tomography. Among the many molecules used in this context are the radioligands [[DASB|[[[Category:Pages with incorrect nuclide templates use]]The element Chemistry:Carbon does not exist.]DASB]] and [[25I-NBOMe|[[[Category:Pages with incorrect nuclide templates use]]The element Chemistry:Carbon does not exist.]Cimbi-5]]. Due to the short half-life, the chemical reactions used to manipulate the radioisotope as generated and incorporate it into a biomolecule must be efficient. Popular key intermediates include [11C]phosgene,[8][9] for carboxylation-related reactions, though other synthons, such as [11C]carbonyl fluoride and [11C]carbon dioxide, are also being explored.[10] For methylation, [11C]iodomethane and related synthons are used.[10]

## Stable isotopes

Main articles: Physics:Carbon-12 and Carbon-13

Carbon-12 and carbon-13 account for approximately 98.9% and 1.1% (respectively) of the naturally occurring carbon on Earth.[11] However, the ratio of stable 13C and 12C in a material can vary due to differences in precursor source and isotopic fractionation induced by a variety of biogeochemical processes. The quantities of the different isotopes are commonly measured via isotope ratio mass spectrometry and expressed as parts per thousand (‰ or "per mille") divergence from the ratio of a standard:[12]

δA13A2213C=((A13A2213CA12A2212C)sample(A13A2213CA12A2212C)standard−1)×1000 ‰

Peedee Belemnite ("PDB"), a fossil belemnite, was the original reference standard used for standardizing isotope ratio values. Due to the depletion of the original PDB, artificial "Vienna PDB", or "VPDB", is generally used today.[13]

### Paleoclimate

The element Chemistry:Carbon does not exist. and The element Chemistry:Carbon does not exist. are measured as the isotope ratio δ13C in benthic foraminifera and used as a proxy for nutrient cycling and the temperature dependent air–sea exchange of CO2 (ventilation).[14] Plants find it easier to use the lighter isotope (The element Chemistry:Carbon does not exist.) when they convert sunlight and carbon dioxide into food. For example, large blooms of plankton (free-floating organisms) absorb large amounts of The element Chemistry:Carbon does not exist. from the oceans. Originally, the The element Chemistry:Carbon does not exist. 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 The element Chemistry:Carbon does not exist. from the surface, leaving the surface layers relatively rich in The element Chemistry:Carbon does not exist.. Where cold waters well up from the depths (such as in the North Atlantic), the water carries The element Chemistry:Carbon does not exist. back up with it; when the ocean was less stratified than today, there was much more The element Chemistry:Carbon does not exist. in the skeletons of surface-dwelling species. Other indicators of past climate include the presence of tropical species and coral growth rings.[15]

### Tracing food sources and diets

Different photosynthetic pathways preferentially select for the lighter The element Chemistry:Carbon does not exist., but their selectivity differs. Grasses in temperate climates (barley, rice, wheat, rye, and oats, plus sunflower, potato, tomatoes, peanuts, cotton, sugar beet, and most trees and their nuts or fruits, roses, and Kentucky bluegrass) follow a C3 photosynthetic pathway that will yield δ13C values averaging about −26.5‰.{{Citation needed|reason=need to p (maize in particular, but also millet, sorghum, sugar cane, and crabgrass) follow a C4 photosynthetic pathway that produces δ13C values averaging about −12.5‰.[16]

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 bone collagen and −14.5‰ in the hydroxylapatite of their teeth and bones.[17]

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. 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).[18]

## Carbon-14

Main article: Physics:Carbon-14

Carbon-14 (also called radiocarbon) occurs in trace amounts and has a half-life of 5700 years. The primary source of The element Chemistry:Carbon does not exist. on Earth is the reaction of The element Chemistry:Nitrogen does not exist. with thermal neutrons from cosmic radiation in the upper atmosphere; this mixes throughout the atmosphere, and biological processes such as photosynthesis incorporate the The element Chemistry:Carbon does not exist. into living organisms. Since organisms stop absorbing The element Chemistry:Carbon does not exist. upon dying, measurement of the amount of The element Chemistry:Carbon does not exist. in a sample may be used to estimate its age. This technique is called radiocarbon dating and is one of the principal methods of radiometric dating in the field of archaeology.

## See also

* Cosmogenic isotopes
* Environmental isotopes
* Isotopic signature
* Radiocarbon dating

Daughter products other than carbon

* Isotopes of nitrogen
* Isotopes of boron
* Isotopes of beryllium
* Isotopes of lithium

## References

1. ↑ Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; De Bièvre, Paul; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry 88 (3): 265–91. doi:10.1515/pac-2015-0305.
2. ↑ 2.0 2.1 "Atomic Weight of Carbon". https://ciaaw.org/carbon.htm.
3. ↑ Scobie, J.; Lewis, G. M. (1 September 1957). "K-capture in carbon 11". Philosophical Magazine 2 (21): 1089–1099. doi:10.1080/14786435708242737. Bibcode: 1957PMag....2.1089S.
4. ↑ 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 of 11C". Nuclear Physics A 96 (2): 279–287. doi:10.1016/0375-9474(67)90712-9. Bibcode: 1967NuPhA..96..279C.
5. ↑ "Carbon-11 Production and Transformation". https://encyclopedia.pub/entry/54549.
6. ↑ Lu, Shuiyu (Jan 18, 2024). "Gas Phase Transformations in Carbon-11 Chemistry". Int. J. Mol. Sci. 25 (2): 1167. doi:10.3390/ijms25021167. PMID 38256240.
7. ↑ Daria Boscolo (2025). "Image-guided treatment of mouse tumours with radioactive ion beams". Nature Physics 21 (10): 1648–1656. doi:10.1038/s41567-025-02993-8. PMID 41098546. Bibcode: 2025NatPh..21.1648B.
8. ↑ "[C-11Phosgene: A Versatile Reagent for Radioactive Carbonyl Insertion Into Medicinal Radiotracers for Positron Emission Tomography"]. https://hero.epa.gov/reference/7421506/.
9. ↑ Nishijima, Ken-Ichi; Kuge, Yuji; Seki, Koh-Ichi; Ohkura, Kazue; Motoki, Noriko; Nagatsu, Kotaro; Tanaka, Akira; Tsukamoto, Eriko et al. (2002). "A simplified and improved synthesis of [11C]phosgene with iron and iron (III) oxide". Nuclear Medicine and Biology 29 (3): 345–350. doi:10.1016/S0969-8051(01)00310-9. PMID 11929705.
10. ↑ 10.0 10.1 Bow, John-Paul J.; Riss, Patrick J. (2021). "Phosgene-Free Carbonyl Insertion: Hot Advances in 11C-Chemistry". Chemistry–Methods 1 (3): 139–141. doi:10.1002/cmtd.202000029.
11. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `CIAAWcarbon`
12. ↑ Miller, Charles B.; Wheeler, Patricia (2012). Biological oceanography (2nd ed.). Chichester, West Sussex: John Wiley & Sons, Ltd.. p. 186. ISBN 9781444333022. OCLC 794619582.
13. ↑ Faure, Gunter; Mensing, Teresa M. (2005). "27 Carbon". Isotopes: Principles and Applications (Third ed.). Hoboken, NJ: Wiley. ISBN 978-81-265-3837-9.
14. ↑ 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. doi:10.1029/95GB02574. Bibcode: 1995GBioC...9..653L. https://boris.unibe.ch/158803/.
15. ↑ Tim Flannery The weather makers: the history & future of climate change, The Text Publishing Company, Melbourne, Australia. ISBN 1-920885-84-6
16. ↑ O'Leary, Marion H. (May 1988). "Carbon Isotopes in Photosynthesis" (in en). BioScience 38 (5): 328–336. doi:10.2307/1310735. https://www.ldeo.columbia.edu/~polissar/OrgGeochem/oleary-1988-carbon-isotopes.pdf. Retrieved 17 November 2022.
17. ↑ Tycot, R. H. (2004). "Stable isotopes and diet: you are what you eat". Proceedings of the International School of Physics "Enrico Fermi" Course CLIV. http://luna.cas.usf.edu/~rtykot/PR39 - Enrico Fermi isotopes.pdf.
18. ↑ Richard, Hedges (2006). "Where does our protein come from?". British Journal of Nutrition 95 (6): 1031–1032. doi:10.1079/bjn20061782. PMID 16768822.

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