Isotopes of cobalt

Naturally occurring cobalt (₂₇Co) consists of a single stable isotope, ⁵⁹Co (thus, cobalt is a mononuclidic element). Twenty-eight radioisotopes have been characterized; the most stable are ⁶⁰Co with a half-life of 5.2714 years, ⁵⁷Co (271.8 days), ⁵⁶Co (77.27 days), and ⁵⁸Co (70.86 days). All other isotopes have half-lives of less than 18 hours and most of these have half-lives of less than 1 second. This element also has 11 meta states, all of which have half-lives of less than 15 minutes.

Isotopes of cobalt (₂₇Co)

Main isotopes^[1] Decay abun­dance half-life (t1/2) mode pro­duct ^56Co synth 77.236 d β^+ ^56Fe ^57Co synth 271.811 d ε ^57Fe ^58Co synth 70.844 d β^+ ^58Fe ^59Co 100% stable ^60Co trace 5.2714 y β^−100% ^60Ni
Standard atomic weight Ar°(Co)
	58.933194±0.000003^[2] 58.933±0.001 (abridged)^[3]
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The isotopes of cobalt range in atomic weight from ⁴⁷Co to ⁷⁵Co. The main decay mode for isotopes with atomic mass less than that of the stable isotope, ⁵⁹Co, is electron capture and the main mode of decay for those of greater than 59 atomic mass units is beta decay. The main decay products before ⁵⁹Co are iron isotopes and the main products after are nickel isotopes.

Radioactive isotopes can be produced by various nuclear reactions. For example, ⁵⁷Co is produced by cyclotron irradiation of iron. The main reaction is the (d,n) reaction ⁵⁶Fe + ²H → n + ⁵⁷Co.^[4]

List of isotopes

Nuclide ^[n 1]	Z	N	Isotopic mass (Da) ^[n 2]^[n 3]	Half-life ^[n 4]	Decay mode ^[n 5]	Daughter isotope ^[n 6]	Spin and parity ^[n 7]^[n 4]	Natural abundance (mole fraction)
	Excitation energy^[n 4]							Normal proportion	Range of variation
^47Co	27	20	47.01149(54)#				7/2−#
^48Co	27	21	48.00176(43)#		p	^47Fe	6+#
^49Co	27	22	48.98972(28)#	<35 ns	p (>99.9%)	^48Fe	7/2−#
					β^+ (<.1%)	^49Fe
^50Co	27	23	49.98154(18)#	44(4) ms	β^+, p (54%)	^49Mn	(6+)
					β^+ (46%)	^50Fe
^51Co	27	24	50.97072(16)#	60# ms [>200 ns]	β^+	^51Fe	7/2−#
^52Co	27	25	51.96359(7)#	115(23) ms	β^+	^52Fe	(6+)
^52mCo	380(100)# keV			104(11)# ms	β^+	^52Fe	2+#
					IT	^52Co
^53Co	27	26	52.954219(19)	242(8) ms	β^+	^53Fe	7/2−#
^53mCo	3197(29) keV			247(12) ms	β^+ (98.5%)	^53Fe	(19/2−)
					p (1.5%)	^52Fe
^54Co	27	27	53.9484596(8)	193.28(7) ms	β^+	^54Fe	0+
^54mCo	197.4(5) keV			1.48(2) min	β^+	^54Fe	(7)+
^55Co	27	28	54.9419990(8)	17.53(3) h	β^+	^55Fe	7/2−
^56Co	27	29	55.9398393(23)	77.233(27) d	β^+	^56Fe	4+
^57Co	27	30	56.9362914(8)	271.74(6) d	EC	^57	7/2−
^58Co	27	31	57.9357528(13)	70.86(6) d	β^+	^58Fe	2+
^58m1Co	24.95(6) keV			9.04(11) h	IT	^58Co	5+
^58m2Co	53.15(7) keV			10.4(3) μs			4+
^59Co	27	32	58.9331950(7)	Stable			7/2−	1.0000
^60Co	27	33	59.9338171(7)	5.2714(6) y	β^−, γ	^60Ni	5+
^60mCo	58.59(1) keV			10.467(6) min	IT (99.76%)	^60Co	2+
					β^− (.24%)	^60Ni
^61Co	27	34	60.9324758(10)	1.650(5) h	β^−	^61Ni	7/2−
^62Co	27	35	61.934051(21)	1.50(4) min	β^−	^62Ni	2+
^62mCo	22(5) keV			13.91(5) min	β^− (99%)	^62Ni	5+
					IT (1%)	^62Co
^63Co	27	36	62.933612(21)	26.9(4) s	β^−	^63Ni	7/2−
^64Co	27	37	63.935810(21)	0.30(3) s	β^−	^64Ni	1+
^65Co	27	38	64.936478(14)	1.20(6) s	β^−	^65Ni	(7/2)−
^66Co	27	39	65.93976(27)	0.18(1) s	β^−	^66Ni	(3+)
^66m1Co	175(3) keV			1.21(1) μs			(5+)
^66m2Co	642(5) keV			>100 μs			(8-)
^67Co	27	40	66.94089(34)	0.425(20) s	β^−	^67Ni	(7/2−)#
^68Co	27	41	67.94487(34)	0.199(21) s	β^−	^68Ni	(7-)
^68mCo	150(150)# keV			1.6(3) s			(3+)
^69Co	27	42	68.94632(36)	227(13) ms	β^− (>99.9%)	^69Ni	7/2−#
					β^−, n (<.1%)	^68Ni
^70Co	27	43	69.9510(9)	119(6) ms	β^− (>99.9%)	^70Ni	(6-)
					β^−, n (<.1%)	^69Ni
^70mCo	200(200)# keV			500(180) ms			(3+)
^71Co	27	44	70.9529(9)	97(2) ms	β^− (>99.9%)	^71Ni	7/2−#
					β^−, n (<.1%)	^70Ni
^72Co	27	45	71.95781(64)#	62(3) ms	β^− (>99.9%)	^72Ni	(6- ,7-)
					β^−, n (<.1%)	^71Ni
^73Co	27	46	72.96024(75)#	41(4) ms			7/2−#
^74Co	27	47	73.96538(86)#	50# ms [>300 ns]			0+
^75Co	27	48	74.96833(86)#	40# ms [>300 ns]			7/2−#
This table header & footer: view

1. ^mCo – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
5. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition
   n:	Neutron emission
   p:	Proton emission

6. Bold symbol as daughter – Daughter product is stable.
7. ( ) spin value – Indicates spin with weak assignment arguments.

Use of cobalt radioisotopes in medicine

Cobalt-57 (⁵⁷Co or Co-57) is used in medical tests; it is used as a radiolabel for vitamin B₁₂ uptake. It is useful for the Schilling test.^[5]

Cobalt-60 (⁶⁰Co or Co-60) is used in radiotherapy. It produces two gamma rays with energies of 1.17 MeV and 1.33 MeV. The ⁶⁰Co source is about 2 cm in diameter and as a result produces a geometric penumbra, making the edge of the radiation field fuzzy. The metal has the unfortunate habit of producing fine dust, causing problems with radiation protection. The ⁶⁰Co source is useful for about 5 years but even after this point is still very radioactive, and so cobalt machines have fallen from favour in the Western world where linacs are common.

Industrial uses for radioactive isotopes

Cobalt-60 (⁶⁰Co) is useful as a gamma ray source because it can be produced in predictable quantities, and for its high radioactivity simply by exposing natural cobalt to neutrons in a reactor.^[6] The uses for industrial cobalt include:

• Sterilization of medical supplies and medical waste
• Radiation treatment of foods for sterilization (cold pasteurization)^[7]
• Industrial radiography (e.g., weld integrity radiographs)
• Density measurements (e.g., concrete density measurements)
• Tank fill height switches

Cobalt-57 is used as a source in Mössbauer spectroscopy of iron-containing samples. Electron capture by ⁵⁷Co forms an excited state of the ⁵⁷Fe nucleus, which in turn decays to the ground state with the emission of a gamma ray. Measurement of the gamma-ray spectrum provides information about the chemical state of the iron atom in the sample.

References

1. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
2. "Standard Atomic Weights: Cobalt". CIAAW. 2017.
3. Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
4. Diaz, L. E. . JPNM Physics Isotopes. University of Harvard. Archived from the original on 2000-10-31. Retrieved 2013-11-15.
5. Diaz, L. E. . JPNM Physics Isotopes. University of Harvard. Archived from the original on 2011-06-11. Retrieved 2010-09-13.
6. "Properties of Cobalt-60". Radioactive Isotopes. Retrieved 2022-12-09.
7. "Beneficial Uses of Cobalt-60". INTERNATIONAL IRRADIATION ASSOCIATION. Retrieved 2022-12-09.

• 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.