Isotopes of chromium

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Naturally occurring chromium (Cr) is composed of three stable isotopes; ⁵²Cr, ⁵³Cr, and ⁵⁴Cr with ⁵²Cr being the most abundant (83.789% natural abundance). Nineteen radioisotopes have been characterized with the most stable being ⁵⁰Cr with a half-life of (more than) 1.8x10¹⁷ years, and ⁵¹Cr with a half-life of 27.7 days. All of the remaining radioactive isotopes have half-lives that are less than 24 hours and the majority of these have half-lives that are less than 1 minute. This element also has 2 meta states.

⁵³Cr is the radiogenic decay product of ⁵³Mn. Chromium isotopic contents are typically combined with manganese isotopic contents and have found application in isotope geology. Mn-Cr isotope ratios reinforce the evidence from ²⁶Al and ¹⁰⁷Pd for the early history of the solar system. Variations in ⁵³Cr/⁵²Cr and Mn/Cr ratios from several meteorites indicate an initial ⁵³Mn/⁵⁵Mn ratio that suggests Mn-Cr isotope systematics must result from in-situ decay of ⁵³Mn in differentiated planetary bodies. Hence ⁵³Cr provides additional evidence for nucleosynthetic processes immediately before coalescence of the solar system.

The isotopes of chromium range in atomic weight from 43 u (⁴³Cr) to 67 u (⁶⁷Cr). The primary decay mode before the most abundant stable isotope, ⁵²Cr, is electron capture and the primary mode after is beta decay.
Standard atomic mass: 51.9961(6) 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)
⁴²Cr	24	18	42.00643(32)#	14(3) ms [13(+4-2) ms]	0+
⁴³Cr	24	19	42.99771(24)#	21.6(7) ms	(3/2+)
⁴⁴Cr	24	20	43.98555(5)#	54(4) ms [53(+4-3) ms]	0+
⁴⁵Cr	24	21	44.97964(54)	50(6) ms	7/2-#
^45mCr	50(100)# keV			1# ms	3/2+#
⁴⁶Cr	24	22	45.968359(21)	0.26(6) s	0+
⁴⁷Cr	24	23	46.962900(15)	500(15) ms	3/2-
⁴⁸Cr	24	24	47.954032(8)	21.56(3) h	0+
⁴⁹Cr	24	25	48.9513357(26)	42.3(1) min	5/2-
⁵⁰Cr	24	26	49.9460442(11)	STABLE [>1.3E+18 a]	0+	0.04345(13)	0.04294-0.04345
⁵¹Cr	24	27	50.9447674(11)	27.7025(24) d	7/2-
⁵²Cr	24	28	51.9405075(8)	STABLE	0+	0.83789(18)	0.83762-0.83790
⁵³Cr	24	29	52.9406494(8)	STABLE	3/2-	0.09501(17)	0.09501-0.09553
⁵⁴Cr	24	30	53.9388804(8)	STABLE	0+	0.02365(7)	0.02365-0.02391
⁵⁵Cr	24	31	54.9408397(8)	3.497(3) min	3/2-
⁵⁶Cr	24	32	55.9406531(20)	5.94(10) min	0+
⁵⁷Cr	24	33	56.943613(2)	21.1(10) s	(3/2-)
⁵⁸Cr	24	34	57.94435(22)	7.0(3) s	0+
⁵⁹Cr	24	35	58.94859(26)	460(50) ms	5/2-#
^59mCr	503.0(17) keV			96(20) µs	(9/2+)
⁶⁰Cr	24	36	59.95008(23)	560(60) ms	0+
⁶¹Cr	24	37	60.95472(27)	261(15) ms	5/2-#
⁶²Cr	24	38	61.95661(36)	199(9) ms	0+
⁶³Cr	24	39	62.96186(32)#	129(2) ms	(1/2-)#
⁶⁴Cr	24	40	63.96441(43)#	43(1) ms	0+
⁶⁵Cr	24	41	64.97016(54)#	27(3) ms	(1/2-)#
⁶⁶Cr	24	42	65.97338(64)#	10(6) ms	0+
⁶⁷Cr	24	43	66.97955(75)#	10# ms [>300 ns]	1/2-#

[edit] Notes

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.