Isotopes of calcium
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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 for all practical purposes it can be considered 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, radioactive 41Ca, which has a half-life of 99,400 years. Unlike cosmogenic isotopes that are produced in the atmosphere, 41Ca is produced by neutron activation of 40Ca. Most of its production is in the upper metre of the soil column, where the cosmogenic neutron flux is still sufficiently strong. 41Ca has received much attention in stellar studies because it decays to 41K, a critical indicator of solar system anomalies. The most stable artificial radioisotopes are 45Ca with a half-life of 163 days and 47Ca with a half-life of 4.5 days. All other calcium isotopes have half-lives measured in minutes or less.[2]
40Ca comprises about 97% of naturally occurring calcium. 40Ca is also one of the daughter products of 40K decay, along with 40Ar. While K–Ar dating has been used extensively in the geological sciences, the prevalence of 40Ca in nature has impeded its use in dating. Techniques using mass spectrometry and a double spike isotope dilution have been used for K–Ca age dating.
List of isotopes[]
Nuclide[3] |
Z | N | Isotopic mass (Da)[4] [n 1] |
Half-life [n 2] |
Decay mode [n 3] |
Daughter isotope [n 4] |
Spin and parity [n 5][n 6] |
Natural abundance (mole fraction) | |||||||||||
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Normal proportion | Range of variation | ||||||||||||||||||
35Ca | 20 | 15 | 35.00514(21)# | 25.7(2) ms | β+, p (95.9%) | 34Ar | 1/2+# | ||||||||||||
β+, 2p (4.1%) | 33Cl | ||||||||||||||||||
36Ca | 20 | 16 | 35.99307(4) | 101.2(15) ms | β+, p (51.2%) | 35Ar | 0+ | ||||||||||||
β+ (48.8%) | 36K | ||||||||||||||||||
37Ca | 20 | 17 | 36.9858979(7) | 181.1(10) ms | β+, p (82.1%) | 36Ar | 3/2+# | ||||||||||||
β+ (17.9%) | 37K | ||||||||||||||||||
38Ca | 20 | 18 | 37.97631923(21) | 443.70(25) ms | β+ | 38K | 0+ | ||||||||||||
39Ca | 20 | 19 | 38.9707108(6) | 860.3(8) ms | β+ | 39K | 3/2+ | ||||||||||||
40Ca[n 7] | 20 | 20 | 39.962590866(22) | Observationally Stable[n 8] | 0+ | 0.96941(156) | 0.96933–0.96947 | ||||||||||||
41Ca | 20 | 21 | 40.96227792(15) | 9.94(15)×104 y | EC | 41K | 7/2− | Trace[n 9] | |||||||||||
42Ca | 20 | 22 | 41.95861783(16) | Stable | 0+ | 0.00647(23) | 0.00646–0.00648 | ||||||||||||
43Ca | 20 | 23 | 42.95876643(24) | Stable | 7/2− | 0.00135(10) | 0.00135–0.00135 | ||||||||||||
44Ca | 20 | 24 | 43.9554815(3) | Stable | 0+ | 0.02086(110) | 0.02082–0.02092 | ||||||||||||
45Ca | 20 | 25 | 44.9561863(4) | 162.61(9) d | β− | 45Sc | 7/2− | ||||||||||||
46Ca | 20 | 26 | 45.9536880(24) | Observationally Stable[n 10] | 0+ | 4(3)×10−5 | 4×10−5–4×10−5 | ||||||||||||
47Ca | 20 | 27 | 46.9545414(24) | 4.536(3) d | β− | 47Sc | 7/2− | ||||||||||||
48Ca[n 11] | 20 | 28 | 47.95252290(10) | (6.4+0.7 −0.6+1.2 −0.9)×1019 a |
β−β−[n 12][n 13] | 48Ti | 0+ | 0.00187(21) | 0.00186–0.00188 | ||||||||||
49Ca | 20 | 29 | 48.95562288(22) | 8.718(6) min | β− | 49Sc | 3/2− | ||||||||||||
50Ca | 20 | 30 | 49.9574992(17) | 13.9(6) s | β− | 50Sc | 0+ | ||||||||||||
51Ca | 20 | 31 | 50.9609957(6) | 10.0(8) s | β− | 51Sc | (3/2−) | ||||||||||||
52Ca | 20 | 32 | 51.9632136(7) | 4.6(3) s | β− (98%) | 52Sc | 0+ | ||||||||||||
β−, n (2%) | 51Sc | ||||||||||||||||||
53Ca | 20 | 33 | 52.96845(5) | 461(90) ms | β− (60%) | 53Sc | 3/2−# | ||||||||||||
β−, n (40%) | 52Sc | ||||||||||||||||||
54Ca | 20 | 34 | 53.97299(5) | 90(6) ms | β− (93%) | 54Sc | 0+ | ||||||||||||
β−, n (7%) | 53Sc | ||||||||||||||||||
55Ca | 20 | 35 | 54.98030(32)# | 22(2) ms | β− | 55Sc | 5/2−# | ||||||||||||
56Ca | 20 | 36 | 55.98508(43)# | 11(2) ms | β− | 56Sc | 0+ | ||||||||||||
57Ca | 20 | 37 | 56.99262(43)# | 5# ms | β− | 57Sc | 5/2−# | ||||||||||||
β−, n | 56Sc | ||||||||||||||||||
58Ca | 20 | 38 | 57.99794(54)# | 3# ms | β− | 58Sc | 0+ | ||||||||||||
β−, n | 57Sc | ||||||||||||||||||
59Ca[6] | 20 | 39 | � | 59Sc | |||||||||||||||
60Ca[6] | 20 | 40 | β− | 60Sc | 0+ | ||||||||||||||
This table header & footer: |
- ^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- ^ Bold half-life – nearly stable, half-life longer than age of universe.
- ^
Modes of decay:
EC: Electron capture
n: Neutron emission p: Proton emission - ^ Bold symbol as daughter – Daughter product is stable.
- ^ ( ) spin value – Indicates spin with weak assignment arguments.
- ^ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
- ^ Heaviest nuclide with equal numbers of protons and neutrons with no observed decay
- ^ Believed to undergo double electron capture to 40Ar with a half-life no less than 5.9×1021 a
- ^ Cosmogenic nuclide
- ^ Believed to undergo β−β− decay to 46Ti with a half-life no less than 2.8×1015 a
- ^ Primordial radionuclide
- ^ Lightest nuclide known to undergo double beta decay
- ^ Theorized to also undergo β− decay to 48Sc with a partial half-life exceeding 1.1+0.8
−0.6×1021 years[5]
References[]
- ^ Meija, Juris; 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.
- ^ Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
- ^ Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001. - ^ Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (2017). "The AME2016 atomic mass evaluation (II). Tables, graphs, and references" (PDF). Chinese Physics C. 41 (3): 030003-1–030003-442. doi:10.1088/1674-1137/41/3/030003.
- ^ Aunola, M.; Suhonen, J.; Siiskonen, T. (1999). "Shell-model study of the highly forbidden beta decay 48Ca → 48Sc". EPL. 46 (5): 577. Bibcode:1999EL.....46..577A. doi:10.1209/epl/i1999-00301-2.
- ^ Jump up to: a b Tarasov, O.B. (2017). "Production of very neutron rich isotopes: What should we know?".
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[]
- Isotopes of calcium
- Calcium
- Lists of isotopes by element