Isotopes of calcium

Main isotopes of Chemistry:calcium (20Ca) | Iso­tope | Decay

|

| abun­dance | half-life (t1/2) | mode | pro­duct
40Ca  | 96.941%  | stable
41Ca  | trace | 9.94×104 y | ε | 41K
42Ca  | 0.647%  | stable
43Ca  | 0.135%  | stable
44Ca  | 2.086%  | stable
45Ca  | syn | 162.6 d  | β− | 45Sc
46Ca  | 0.004%  | stable
47Ca  | syn  | 4.5 d  | β− | 47Sc
γ | –
48Ca | 0.187%  | 6.4×1019 y  | β−β− | 48Ti
Standard atomic weight Ar, standard(Ca)|

* 40.078(4)[1]

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Calcium (20Ca) has 26 known isotopes, ranging from 35Ca to 60Ca. There are five stable isotopes (40Ca, 42Ca, 43Ca, 44Ca and 46Ca), plus one isotope (48Ca) with such a long half-life that it is for all practical purposes stable. The most abundant isotope, 40Ca, as well as the rare 46Ca, are theoretically unstable on energetic grounds, but their decay has not been observed. Calcium also has a cosmogenic isotope, 41Ca, with half-life 99,400 years. Unlike cosmogenic isotopes produced in the air, 41Ca is produced by neutron activation of solid 40Ca in rock and soil. Most of its production is in the upper metre of the soil column, where the cosmogenic neutron flux is still strong enough. The most stable artificial isotopes are 45Ca with half-life 162.61 days and 47Ca with half-life 4.536 days. All other calcium isotopes have half-lives of minutes or less.

40Ca comprises about 97% of natural calcium and is mainly created by nucleosynthesis in stars (alpha process). Like 40Ar, however, some 40Ca is radiogenic, created by radioactive decay of 40K. While K–Ar dating has been used extensively in the geological sciences, the prevalence of 40Ca in nature initially impeded the proliferation of K-Ca dating in early studies, with only a handful of studies in the 20th century. Modern techniques using increasingly precise Thermal-Ionization (TIMS) and Collision-Cell Multi-Collector Inductively-coupled plasma mass spectrometry (CC-MC-ICP-MS) techniques, however, have been used for successful K–Ca dating[2][3] similar in method to Rb-Sr dating, as well as determining K losses from the lower continental crust[4] and for source-tracing calcium contributions from various geologic reservoirs.[5][6]

Stable isotope variations of calcium (most typically 44Ca/40Ca or 44Ca/42Ca, denoted 'δ44Ca' and 'δ44/42Ca' in delta notation) are also widely used across the natural sciences for a number of applications, ranging from early determination of osteoporosis[7] to quantifying volcanic eruption timescales.[8] Other applications include: quantifying carbon sequestration efficiency in CO2 injection sites[9] and understanding ocean acidification,[10] exploring both ubiquitous and rare magmatic processes, such as formation of granites[11] and carbonatites,[12] tracing modern and ancient trophic webs including in dinosaurs,[13][14][15] assessing weaning practices in ancient humans,[16] and a plethora of other emerging applications.

## Contents

* 1 List of isotopes
* 2 Calcium-48
* 3 Calcium-60
* 4 See also
* 5 References
* 6 Further reading
* 7 External links

## List of isotopes

Nuclide
| Z | N | Isotopic mass (u)
[n 1] | Half-life
[n 2] | Decay
mode
[n 3] | Daughter
isotope
[n 4] | Spin and
parity
[n 5][n 6] | Physics:Natural abundance (mole fraction)

|
|
|
|
|
|
|
|

Normal proportion  | Range of variation
35Ca  | 20  | 15  | 35.00557(22)#  | 1985 | 25.7(2) ms  | β+, p (95.8%)  | 34Ar  | 1/2+#  |  |
β+, 2p (4.2%)  | 33Cl
β+ (rare)  | 35K
36Ca  | 20  | 16  | 35.993074(43)  | 1977 | 100.9(13) ms  | β+, p (51.2%)  | 35Ar  | 0+  |  |
β+ (48.8%)  | 36K
37Ca  | 20  | 17  | 36.98589785(68)  | 1964 | 181.0(9) ms  | β+, p (76.8%)  | 36Ar | 3/2+  |  |
β+ (23.2%)  | 37K
38Ca  | 20  | 18  | 37.97631922(21)  | 1966 | 443.70(25) ms  | β+ | 38K  | 0+  |  |
39Ca  | 20  | 19  | 38.97071081(64)  | 1943 | 860.3(8) ms  | β+ | 39K | 3/2+  |  |
40Ca[n 7] | 20  | 20  | 39.962590850(22)  | 1922 | Observationally stable[n 8] | 0+  | 0.9694(16)  | 0.96933–0.96947
41Ca  | 20  | 21  | 40.96227791(15)  | 1939 | 9.94(15)×104 y  | EC | 41K | 7/2−  | Trace[n 9] |
42Ca  | 20  | 22  | 41.95861778(16)  | 1934 | Stable | 0+  | 0.00647(23)  | 0.00646–0.00648
43Ca  | 20  | 23  | 42.95876638(24)  | 1934 | Stable | 7/2−  | 0.00135(10)  | 0.00135–0.00135
44Ca  | 20  | 24  | 43.95548149(35)  | 1922 | Stable | 0+  | 0.0209(11)  | 0.02082–0.02092
45Ca  | 20  | 25  | 44.95618627(39)  | 1940 | 162.61(9) d  | β− | 45Sc | 7/2−  |  |
46Ca  | 20  | 26  | 45.9536877(24)  | 1938 | Observationally stable[n 10] | 0+  | 4×10−5 | 4×10−5–4×10−5
47Ca  | 20  | 27  | 46.9545411(24)  | 1951 | 4.536(3) d  | β− | 47Sc  | 7/2−  |  |
48Ca[n 11][n 12] | 20  | 28  | 47.952522654(18)  | 1938 | 5.6(10)×1019 y | β−β−[n 13][n 14] | 48Ti | 0+  | 0.00187(21)  | 0.00186–0.00188
49Ca  | 20  | 29  | 48.95566263(19)  | 1950 | 8.718(6) min  | β− | 49Sc  | 3/2−  |  |
50Ca  | 20  | 30  | 49.9574992(17)  | 1964 | 13.45(5) s  | β− | 50Sc  | 0+  |  |
51Ca  | 20  | 31  | 50.96099566(56)  | 1980 | 10.0(8) s  | β− | 51Sc  | 3/2−  |  |
52Ca  | 20  | 32  | 51.96321365(72)  | 1985 | 4.6(3) s  | β− (>98%)  | 52Sc  | 0+  |  |
β−, n (<2%)  | 51Sc
53Ca  | 20  | 33  | 52.968451(47)  | 1983 | 461(90) ms  | β− (60%)  | 53Sc  | 1/2−#  |  |
β−, n (40%)  | 52Sc
54Ca  | 20  | 34  | 53.972989(52)  | 1997 | 90(6) ms  | β− | 54Sc  | 0+  |  |
55Ca  | 20  | 35  | 54.97998(17)  | 1997 | 22(2) ms  | β− | 55Sc  | 5/2−#  |  |
56Ca  | 20  | 36  | 55.98550(27)  | 1997 | 11(2) ms  | β− | 56Sc  | 0+  |  |
57Ca  | 20  | 37  | 56.99296(43)#  | 2009 | 8# ms [>620 ns]  |  |  | 5/2−#  |  |
58Ca  | 20  | 38  | 57.99836(54)#  | 2009 | 4# ms [>620 ns]  |  |  | 0+  |  |
59Ca  | 20  | 39  | 59.00624(64)#  | 2018 | 5# ms [>400 ns]  |  |  | 5/2−#  |  |
60Ca  | 20  | 40  | 60.01181(75)#  | 2018 | 2# ms [>400 ns]  |  |  | 0+  |  |
61Ca  | 20  | 41  | 61.02041(86)#  | (2025)[18][n 15] | 1# ms  |  |  | 1/2−#  |

1. ↑ ( ) - Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
2. ↑ Bold half-life - nearly stable, half-life longer than age of universe.
3. ↑ Modes of decay:  EC: | Electron capture

|

n: | Neutron emission
p: | Proton emission
4. ↑ Bold symbol as daughter - Daughter product is stable.
5. ↑ ( ) spin value - Indicates spin with weak assignment arguments.
6. ↑ # - Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
7. ↑ Heaviest observationally stable nuclide with equal numbers of protons and neutrons
8. ↑ Believed to undergo double electron capture to 40Ar with a half-life no less than 1022 y
9. ↑ Cosmogenic nuclide
10. ↑ Believed to undergo β−β− decay to 46Ti
11. ↑ Primordial radionuclide
12. ↑ Believed to be capable of undergoing triple beta decay with very long partial half-life
13. ↑ Lightest nuclide known to undergo double beta decay
14. ↑ Theorized to also undergo β− decay to 48Sc with a partial half-life exceeding 1.1+0.8−0.6×1021 years[17]
15. ↑ Discovery of this isotope is unconfirmed

## Calcium-48

Main article: Physics:Calcium-48

About 2 g of calcium-48

Calcium-48 is a doubly magic nucleus with 28 neutrons; unusually neutron-rich for a light primordial nucleus. It decays via double beta decay with an extremely long half-life of about 5.6×1019 years, though single beta decay is also theoretically possible. This decay can analyzed with the sd nuclear shell model, and it is more energetic (4.27 MeV) than any other double beta decay.[19] It is used as a precursor for neutron-rich[20] and superheavy[21] isotopes.

## Calcium-60

Calcium-60 is the heaviest known isotope as of 2020[update].[22] First observed in 2018 at Riken alongside 59Ca and seven isotopes of other elements,[23] its existence suggests that there are additional even-N isotopes of calcium up to at least 70Ca, while 59Ca is probably the last bound isotope with odd N.[24] Earlier predictions had estimated the heaviest even isotope to be at 60Ca, and 59Ca unbound.[23]

In the neutron-rich region, N = 40 becomes a magic number, so 60Ca was considered early on to be a possibly doubly magic nucleus, as is observed for the 68Ni isotone.[25][26] However, subsequent spectroscopic measurements of the nearby nuclides 56Ca, 58Ca, and 62Ti instead predict that it should lie on the island of inversion known to exist around 64Cr.[26][27]

## See also

Daughter products other than calcium

* Isotopes of titanium
* Isotopes of scandium
* Isotopes of potassium
* Isotopes of argon

## 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. ↑ Marshall, B. D.; DePaolo, D. J. (1982-12-01). "Precise age determinations and petrogenetic studies using the KCa method". Geochimica et Cosmochimica Acta 46 (12): 2537–2545. doi:10.1016/0016-7037(82)90376-3. ISSN 0016-7037. Bibcode: 1982GeCoA..46.2537M. [clarification needed]
3. ↑ admin (18 January 2023). "K-Ca dating and Ca isotope composition of the oldest Solar System lava, Erg Chech 002" (in en-US). Geochemical Perspectives Letters 24 (24): 33–37. doi:10.7185/geochemlet.2302. Bibcode: 2023GChPL..24...33D. https://www.geochemicalperspectivesletters.org/article2302/. Retrieved 2024-10-16.
4. ↑ admin (6 February 2019). "Radiogenic Ca isotopes confirm post-formation K depletion of lower crust | Geochemical Perspectives Letters" (in en-US). Geochemical Perspectives Letters 9 (9): 43–48. https://www.geochemicalperspectivesletters.org/article1904/. Retrieved 2024-10-16.
5. ↑ Antonelli, Michael A.; DePaolo, Donald J.; Christensen, John N.; Wotzlaw, Jörn-Frederik; Pester, Nicholas J.; Bachmann, Olivier (2021-09-16). "Radiogenic 40 Ca in Seawater: Implications for Modern and Ancient Ca Cycles" (in en). ACS Earth and Space Chemistry 5 (9): 2481–2492. doi:10.1021/acsearthspacechem.1c00179. ISSN 2472-3452. Bibcode: 2021ESC.....5.2481A. https://pubs.acs.org/doi/10.1021/acsearthspacechem.1c00179.
6. ↑ Davenport, Jesse; Caro, Guillaume; France-Lanord, Christian (2022-12-01). "Decoupling of physical and chemical erosion in the Himalayas revealed by radiogenic Ca isotopes". Geochimica et Cosmochimica Acta 338: 199–219. doi:10.1016/j.gca.2022.10.031. ISSN 0016-7037. Bibcode: 2022GeCoA.338..199D.
7. ↑ Eisenhauer, A.; Müller, M.; Heuser, A.; Kolevica, A.; Glüer, C. -C.; Both, M.; Laue, C.; Hehn, U. v. et al. (2019-06-01). "Calcium isotope ratios in blood and urine: A new biomarker for the diagnosis of osteoporosis". Bone Reports 10. doi:10.1016/j.bonr.2019.100200. ISSN 2352-1872. PMID 30997369.
8. ↑ Antonelli, Michael A.; Mittal, Tushar; McCarthy, Anders; Tripoli, Barbara; Watkins, James M.; DePaolo, Donald J. (2019-10-08). "Ca isotopes record rapid crystal growth in volcanic and subvolcanic systems" (in en). Proceedings of the National Academy of Sciences 116 (41): 20315–20321. doi:10.1073/pnas.1908921116. ISSN 0027-8424. PMID 31548431. Bibcode: 2019PNAS..11620315A.
9. ↑ Pogge von Strandmann, Philip A. E.; Burton, Kevin W.; Snæbjörnsdóttir, Sandra O.; Sigfússon, Bergur; Aradóttir, Edda S.; Gunnarsson, Ingvi; Alfredsson, Helgi A.; Mesfin, Kiflom G. et al. (2019-04-30). "Rapid CO2 mineralisation into calcite at the CarbFix storage site quantified using calcium isotopes" (in en). Nature Communications 10 (1): 1983. doi:10.1038/s41467-019-10003-8. ISSN 2041-1723. PMID 31040283.
10. ↑ Fantle, Matthew S.; Ridgwell, Andy (2020-08-05). "Towards an understanding of the Ca isotopic signal related to ocean acidification and alkalinity overshoots in the rock record". Chemical Geology 547. doi:10.1016/j.chemgeo.2020.119672. ISSN 0009-2541. Bibcode: 2020ChGeo.54719672F.
11. ↑ Antonelli, Michael A.; Yakymchuk, Chris; Schauble, Edwin A.; Foden, John; Janoušek, Vojtěch; Moyen, Jean-François; Hoffmann, Jan; Moynier, Frédéric et al. (2023-04-15). "Granite petrogenesis and the δ44Ca of continental crust". Earth and Planetary Science Letters 608. doi:10.1016/j.epsl.2023.118080. ISSN 0012-821X. https://www.sciencedirect.com/science/article/pii/S0012821X23000936.
12. ↑ admin (December 2023). "Calcium isotope fractionation during melt immiscibility and carbonatite petrogenesis | Geochemical Perspectives Letters" (in en-US). Geochemical Perspectives Letters 28 (28): 13–19. doi:10.7185/geochemlet.2338. https://www.geochemicalperspectivesletters.org/article2338/. Retrieved 2024-10-16.
13. ↑ Skulan, Joseph; DePaolo, Donald J.; Owens, Thomas L. (1997-06-01). "Biological control of calcium isotopic abundances in the global calcium cycle". Geochimica et Cosmochimica Acta 61 (12): 2505–2510. doi:10.1016/S0016-7037(97)00047-1. ISSN 0016-7037. Bibcode: 1997GeCoA..61.2505S. https://www.sciencedirect.com/science/article/abs/pii/S0016703797000471.
14. ↑ admin (26 April 2019). "Calcium stable isotopes place Devonian conodonts as first level consumers | Geochemical Perspectives Letters" (in en-US). Geochemical Perspectives Letters 10 (10): 36–39. https://www.geochemicalperspectivesletters.org/article1912/. Retrieved 2024-10-16.
15. ↑ Hassler, A.; Martin, J. E.; Amiot, R.; Tacail, T.; Godet, F. Arnaud; Allain, R.; Balter, V. (2018-04-11). "Calcium isotopes offer clues on resource partitioning among Cretaceous predatory dinosaurs" (in en). Proceedings of the Royal Society B: Biological Sciences 285 (1876). doi:10.1098/rspb.2018.0197. ISSN 0962-8452. PMID 29643213.
16. ↑ Tacail, Théo; Thivichon-Prince, Béatrice; Martin, Jeremy E.; Charles, Cyril; Viriot, Laurent; Balter, Vincent (2017-06-13). "Assessing human weaning practices with calcium isotopes in tooth enamel" (in en). Proceedings of the National Academy of Sciences 114 (24): 6268–6273. doi:10.1073/pnas.1704412114. ISSN 0027-8424. PMID 28559355. Bibcode: 2017PNAS..114.6268T.
17. ↑ Aunola, M.; Suhonen, J.; Siiskonen, T. (1999). "Shell-model study of the highly forbidden beta decay 48Ca → 48Sc". EPL 46 (5): 577. doi:10.1209/epl/i1999-00301-2. Bibcode: 1999EL.....46..577A.
18. ↑ Tarasov, O. B.; Sherrill, B. M.; Dombos, A. C.; Fukushima, K.; Gade, A.; Haak, K.; Hausmann, M.; Kahl, D. et al. (4 September 2025). "Discovery of new isotopes in the fragmentation of Se 82 and insights into their production". Physical Review C 112 (3). doi:10.1103/573p-7fjp.
19. ↑ Balysh, A. (1996). "Double Beta Decay of 48Ca". Physical Review Letters 77 (26): 5186–5189. doi:10.1103/PhysRevLett.77.5186. PMID 10062737. Bibcode: 1996PhRvL..77.5186B.
20. ↑ Notani, M. (2002). "New neutron-rich isotopes, 34Ne, 37Na and 43Si, produced by fragmentation of a 64A MeV 48Ca beam". Physics Letters B 542 (1–2): 49–54. doi:10.1016/S0370-2693(02)02337-7. Bibcode: 2002PhLB..542...49N.
21. ↑ Oganessian, Yu. Ts. (October 2006). "Synthesis of the isotopes of elements 118 and 116 in the 249Cf and 245Cm + 48Ca fusion reactions". Physical Review C 74 (4). doi:10.1103/PhysRevC.74.044602. Bibcode: 2006PhRvC..74d4602O.
22. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `NUBASE2020`
23. ↑ 23.0 23.1 Tarasov, O. B.; Ahn, D. S.; Bazin, D. et al. (11 July 2018). "Discovery of 60Ca and Implications For the Stability of 70Ca". Physical Review Letters 121 (2). doi:10.1103/PhysRevLett.121.022501. PMID 30085743.
24. ↑ Neufcourt, Léo; Cao, Yuchen; Nazarewicz, Witold et al. (14 February 2019). "Neutron Drip Line in the Ca Region from Bayesian Model Averaging". Physical Review Letters 122 (6). doi:10.1103/PhysRevLett.122.062502. PMID 30822058. Bibcode: 2019PhRvL.122f2502N.
25. ↑ Gade, A.; Janssens, R. V. F.; Weisshaar, D. et al. (21 March 2014). "Nuclear Structure Towards N = 40 60Ca: In-Beam γ -Ray Spectroscopy of 58, 60Ti". Physical Review Letters 112 (11). doi:10.1103/PhysRevLett.112.112503. PMID 24702356.
26. ↑ 26.0 26.1 Cortés, M.L.; Rodriguez, W.; Doornenbal, P. et al. (January 2020). "Shell evolution of N = 40 isotones towards 60Ca: First spectroscopy of 62Ti". Physics Letters B 800. doi:10.1016/j.physletb.2019.135071.
27. ↑ Chen, S.; Browne, F.; Doornenbal, P. et al. (August 2023). "Level structures of 56, 58Ca cast doubt on a doubly magic 60Ca". Physics Letters B 843. doi:10.1016/j.physletb.2023.138025.

## Further reading

* C. Michael Hogan. 2010. Calcium. ed. A. Jorgenson and C. Cleveland. Encyclopedia of Earth, National Council for Science and the Environment, Washington, D.C.

## External links

* Calcium isotopes data from The Berkeley Laboratory Isotopes Project's

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