Isotopes of chromium

Main isotopes of chromium (₂₄Cr)
γ	–
Standard atomic weight (Ar, standard)	51.9961(6)[1];

Naturally occurring chromium (₂₄Cr) is composed of four stable isotopes; ⁵⁰Cr, ⁵²Cr, ⁵³Cr, and ⁵⁴Cr with ⁵²Cr being the most abundant (83.789% natural abundance). ⁵⁰Cr is suspected of decaying by β⁺β⁺ to ⁵⁰Ti with a half-life of (more than) 1.8×10¹⁷ years. Twenty-two radioisotopes, all of which are entirely synthetic, have been characterized with the most stable being 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, the least stable being ⁶⁶Cr with a half-life of 10 milliseconds. This element also has 2 meta states, ^45mCr, the more stable one, and ^59mCr, the least stable isotope or isomer.

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 same isotope is preferentially involved in certain leaching reactions, thereby allowing its abundance in seawater sediments to be used as a proxy for atmospheric oxygen concentrations.^[2]

The isotopes of chromium range from ⁴²Cr to ⁶⁷Cr. The primary decay mode before the most abundant stable isotope, ⁵²Cr, is electron capture and the primary mode after is beta decay.

List of isotopes

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)^[3]^{[n 1]}	daughter isotope(s)^{[n 2]}	nuclear spin and parity	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
nuclide symbol	excitation energy			half-life	decay mode(s)^[3]^{[n 1]}	daughter isotope(s)^{[n 2]}	nuclear spin and parity	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
⁴²Cr	24	18	42.00643(32)#	14(3) ms [13(+4-2) ms]	β⁺ (>99.9%)	⁴²V	0+
⁴²Cr	24	18	42.00643(32)#	14(3) ms [13(+4-2) ms]	2p (<.1%)	⁴⁰Ti	0+
⁴³Cr	24	19	42.99771(24)#	21.6(7) ms	β⁺ (71%)	⁴³V	(3/2+)
					β⁺, p (23%)	⁴²Ti
					β⁺, 2p (6%)	⁴¹Sc
					β⁺, α (<.1%)	³⁹Sc
⁴⁴Cr	24	20	43.98555(5)#	54(4) ms [53(+4-3) ms]	β⁺ (93%)	⁴⁴V	0+
⁴⁴Cr	24	20	43.98555(5)#	54(4) ms [53(+4-3) ms]	β⁺, p (7%)	⁴³Ti	0+
⁴⁵Cr	24	21	44.97964(54)	50(6) ms	β⁺ (73%)	⁴⁵V	7/2−#
⁴⁵Cr	24	21	44.97964(54)	50(6) ms	β⁺, p (27%)	⁴⁴Ti	7/2−#
^45mCr	50(100)# keV			1# ms	IT	⁴⁵Cr	3/2+#
^45mCr	50(100)# keV			1# ms	β⁺	⁴⁵V	3/2+#
⁴⁶Cr	24	22	45.968359(21)	0.26(6) s	β⁺	⁴⁶V	0+
⁴⁷Cr	24	23	46.962900(15)	500(15) ms	β⁺	⁴⁷V	3/2−
⁴⁸Cr	24	24	47.954032(8)	21.56(3) h	β⁺	⁴⁸V	0+
⁴⁹Cr	24	25	48.9513357(26)	42.3(1) min	β⁺	⁴⁹V	5/2−
⁵⁰Cr	24	26	49.9460442(11)	Observationally Stable^{[n 3]}			0+	0.04345(13)	0.04294–0.04345
⁵¹Cr	24	27	50.9447674(11)	27.7025(24) d	EC	⁵¹V	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	β⁻	⁵⁵Mn	3/2−
⁵⁶Cr	24	32	55.9406531(20)	5.94(10) min	β⁻	⁵⁶Mn	0+
⁵⁷Cr	24	33	56.943613(2)	21.1(10) s	β⁻	⁵⁷Mn	(3/2−)
⁵⁸Cr	24	34	57.94435(22)	7.0(3) s	β⁻	⁵⁸Mn	0+
⁵⁹Cr	24	35	58.94859(26)	460(50) ms	β⁻	⁵⁹Mn	5/2−#
^59mCr	503.0(17) keV			96(20) µs			(9/2+)
⁶⁰Cr	24	36	59.95008(23)	560(60) ms	β⁻	⁶⁰Mn	0+
⁶¹Cr	24	37	60.95472(27)	261(15) ms	β⁻ (>99.9%)	⁶¹Mn	5/2−#
⁶¹Cr	24	37	60.95472(27)	261(15) ms	β⁻, n (<.1%)	⁶⁰Mn	5/2−#
⁶²Cr	24	38	61.95661(36)	199(9) ms	β⁻ (>99.9%)	⁶²Mn	0+
⁶²Cr	24	38	61.95661(36)	199(9) ms	β⁻, n	⁶¹Mn	0+
⁶³Cr	24	39	62.96186(32)#	129(2) ms	β⁻	⁶³Mn	(1/2−)#
⁶³Cr	24	39	62.96186(32)#	129(2) ms	β⁻, n	⁶²Mn	(1/2−)#
⁶⁴Cr	24	40	63.96441(43)#	43(1) ms	β⁻	⁶⁴Mn	0+
⁶⁵Cr	24	41	64.97016(54)#	27(3) ms	β⁻	⁶⁵Mn	(1/2−)#
⁶⁶Cr	24	42	65.97338(64)#	10(6) ms	β⁻	⁶⁶Mn	0+
⁶⁷Cr	24	43	66.97955(75)#	10# ms [>300 ns]	β⁻	⁶⁷Mn	1/2−#

↑ Abbreviations:
EC: Electron capture
IT: Isomeric transition
↑ Bold for stable isotopes
↑ Suspected of decaying by double electron capture to ⁵⁰Ti with a half-life of no less than 1.3×10¹⁸ a

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.
Nuclide masses are given by IUPAP Commission on Symbols, Units, Nomenclature, Atomic Masses and Fundamental Constants (SUNAMCO)
Isotope abundances are given by IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW)

References

↑ Meija, J.; 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.
↑ R. Frei; C. Gaucher; S. W. Poulton; D. E. Canfield (2009). "Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes". Nature. 461 (7261): 250–3. Bibcode:2009Natur.461..250F. doi:10.1038/nature08266. PMID 19741707.
↑ "Universal Nuclide Chart". nucleonica. (Registration required (help)).

Isotope masses from:
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23.
Isotopic compositions and standard atomic masses from:
- J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23.
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved 23 February 2017.
- N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.

External links

Chromium isotopes data from The Berkeley Laboratory Isotopes Project's

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[4] Abbreviations:
EC: Electron capture
IT: Isomeric transition

[5] Bold for stable isotopes

[6] Suspected of decaying by double electron capture to ⁵⁰Ti with a half-life of no less than 1.3×10¹⁸ a

[CIAAW2016-1] Meija, J.; 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] R. Frei; C. Gaucher; S. W. Poulton; D. E. Canfield (2009). "Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes". Nature. 461 (7261): 250–3. Bibcode:2009Natur.461..250F. doi:10.1038/nature08266. PMID 19741707.

[3] "Universal Nuclide Chart". nucleonica. (Registration required (help)).