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Chromium-51

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Chromium-51

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Main isotopes			Decay
	abundance	half-life (t_1/2)	mode	product
⁵⁰Cr	4.34%	stable
⁵¹Cr	synth	27.7025 d	ε	⁵¹V
⁵¹Cr	synth	27.7025 d	γ	–
⁵²Cr	83.8%	stable
⁵³Cr	9.50%	stable
⁵⁴Cr	2.37%	stable

Standard atomic weight A_r°(Cr)

51.9961±0.0006
51.996±0.001 (abridged)

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, 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. This element also has two 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.

The isotopes of chromium range from ⁴²Cr to ⁷⁰Cr. 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	Z	N	Isotopic mass (Da)	Half-life	Decay mode	Daughter isotope	Spin and parity	Natural abundance (mole fraction)
Nuclide	Excitation energy			Half-life	Decay mode	Daughter isotope	Spin and parity	Normal proportion	Range of variation
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			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−#
⁶⁸Cr	24	44	67.98316(54)#	10# ms (>620 ns)	β⁻?	⁶⁸Mn	0+
					β⁻, n?	⁶⁷Mn
					β⁻, 2n?	⁶⁶Mn
⁶⁹Cr	24	45	68.98966(54)#	6# ms (>620 ns)	β⁻?	⁶⁹Mn	7/2+#
					β⁻, n?	⁶⁸Mn
					β⁻, 2n?	⁶⁷Mn
⁷⁰Cr	24	46	69.99395(64)#	6# ms (>620 ns)	β⁻?	⁷⁰Mn	0+
					β⁻, n?	⁶⁹Mn
					β⁻, 2n?	⁶⁸Mn
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Chromium-51

Chromium-51 is a synthetic radioactive isotope of chromium having a half-life of 27.7 days and decaying by electron capture with emission of gamma rays (0.32 MeV); it is used to label red blood cells for measurement of mass or volume, survival time, and sequestration studies, for the diagnosis of gastrointestinal bleeding, and to label platelets to study their survival. It has a role as a radioactive label. Chromium Cr-51 has been used as a radioactive label for decades. It is used as a diagnostic radiopharmaceutical agent in nephrology to determine glomerular filtration rate, and in hematology to determine red blood cell volume or mass, study the red blood cell survival time and evaluate blood loss.

External links

Chromium isotopes data from The Berkeley Laboratory Isotopes Project's

Isotope masses from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
Isotopic compositions and standard atomic masses from:
- de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
"News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
Half-life, spin, and isomer data selected from the following sources.
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
- Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.