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Isotopes of calcium



Calcium (Ca) has four stable isotopes (40Ca and 42Ca through 44Ca), plus two more isotopes (46Ca and 48Ca) that have such long half-lives that for all practical purposes they can be considered stable. It also has a cosmogenic isotope, radioactive 41Ca, which has a half-life of 103,000 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 or so 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.

Additional recommended knowledge

97% of naturally occurring calcium is in the form of 40Ca. 40Ca is 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.


Standard atomic mass: 40.078(4) u

Table

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
34Ca 20 14 34.01412(32)# <35 ns 0+
35Ca 20 15 35.00494(21)# 25.7(2) ms 1/2+#
36Ca 20 16 35.99309(4) 102(2) ms 0+
37Ca 20 17 36.985870(24) 181.1(10) ms (3/2+)
38Ca 20 18 37.976318(5) 440(8) ms 0+
39Ca 20 19 38.9707197(20) 859.6(14) ms 3/2+
40Ca 20 20 39.96259098(22) STABLE [>5.9E+21 a] 0+ 0.96941(156) 0.96933-0.96947
41Ca 20 21 40.96227806(26) 1.02(7)E+5 a 7/2-
42Ca 20 22 41.95861801(27) STABLE 0+ 0.00647(23) 0.00646-0.00648
43Ca 20 23 42.9587666(3) STABLE 7/2- 0.00135(10) 0.00135-0.00135
44Ca 20 24 43.9554818(4) STABLE 0+ 0.02086(110) 0.02082-0.02092
45Ca 20 25 44.9561866(4) 162.67(25) d 7/2-
46Ca 20 26 45.9536926(24) STABLE [>100E+15 a] 0+ 0.00004(3) 0.00004-0.00004
47Ca 20 27 46.9545460(24) 4.536(3) d 7/2-
48Ca 20 28 47.952534(4) 43(38)E+18 a 0+ 0.00187(21) 0.00186-0.00188
49Ca 20 29 48.955674(4) 8.718(6) min 3/2-
50Ca 20 30 49.957519(10) 13.9(6) s 0+
51Ca 20 31 50.9615(1) 10.0(8) s (3/2-)#
52Ca 20 32 51.96510(75) 4.6(3) s 0+
53Ca 20 33 52.97005(54)# 90(15) ms 3/2-#
54Ca 20 34 53.97435(75)# 50# ms [>300 ns] 0+
55Ca 20 35 54.98055(75)# 30# ms [>300 ns] 5/2-#
56Ca 20 36 55.98557(97)# 10# ms [>300 ns] 0+
57Ca 20 37 56.99236(107)# 5# ms 5/2-#

Notes

  • Evaluated isotopic composition is for most but not all commercial samples.
  • The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
  • Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References

  • Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
  • Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
  • Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
    • Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
    • National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
    • David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.


Isotopes of potassium Isotopes of calcium Isotopes of scandium
Index to isotope pages
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Isotopes_of_calcium". A list of authors is available in Wikipedia.
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