Isotopes of cobalt

Naturally occurring cobalt (Co) is composed of 1 stable isotope, ⁵⁹Co. 28 radioisotopes have been characterized with the most stable being ⁶⁰Co with a half-life of 5.2714 years, ⁵⁷Co with a half-life of 271.8 days, ⁵⁶Co with a half-life of 77.27 days, and ⁵⁸Co with a half-life of 70.86 days. All of the remaining radioactive isotopes have half-lives that are less than 18 hours and the majority of these have half-lives that are less than 1 second. This element also has 11 meta states, all of which have half-lives less than 15 minutes.

The isotopes of cobalt range in atomic weight from ⁴⁷Co to ⁷⁵Co. The primary decay mode for isotopes with atomic mass unit values less than that of the most abundant stable isotope, ⁵⁹Co, is electron capture and the primary mode of decay for those of greater than 59 atomic mass units is beta decay. The primary decay products before ⁵⁹Co are iron isotopes and the primary products after are nickel isotopes.

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

Relative atomic mass of cobalt: 58.933195(5)

Use of cobalt radioisotopes in medicine

Cobalt-60 (Co-60 or ⁶⁰Co) is a radioactive metal that 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 a 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 favor in the Western world where linacs are common.

Cobalt-57 (Co-57 or ⁵⁷Co) is a radioactive metal that is used in medical tests; it is used as a radiolabel for vitamin B₁₂ uptake. It is useful for the Schilling test.

Industrial uses for radioactive isotopes

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

• Sterilization of medical supplies and medical waste
• Radiation treatment of foods for sterilization (cold pasteurization)
• 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. The electron capture decay of the ⁵⁷Co forms an excited state of the ⁵⁷Fe nucleus, which in turn decays to the ground state with emission of a gamma ray. Measurement of the gamma ray spectrum provides information about the chemical state of the iron atom in the sample.

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
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	57Fe	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)	5.2713(8) 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−#

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

References

• Isotope masses from:
• Isotopic compositions and standard atomic masses from:
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
  • 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.

Isotopes of iron	Isotopes of cobalt	Isotopes of nickel
Table of nuclides