Isotopes of calcium

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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.

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

1 Table
- 1.1 Notes
2 References
3 External links

[edit] 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)
nuclide symbol	excitation energy			half-life	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
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-#

[edit] 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.

[edit] 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.