Isotopes of cobalt

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Isotopes of cobalt  (27Co)
Main isotopes [1] Decay
abun­dance half-life (t1/2) mode pro­duct
56Co synth 77.236 d β+ 56Fe
57Cosynth271.811 d ε 57Fe
58Cosynth70.844 dβ+ 58Fe
59Co100% stable
60Co trace 5.2714 y β− 100% 60Ni
Standard atomic weight Ar°(Co)

Naturally occurring cobalt, Co, 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.

Contents

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.

Radioisotopes 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 proportionRange of variation
47Co272047.01149(54)#7/2−#
48Co272148.00176(43)# p 47Fe6+#
49Co272248.98972(28)#<35 nsp (>99.9%)48Fe7/2−#
β+ (<.1%)49Fe
50Co272349.98154(18)#44(4) msβ+, p (54%)49Mn(6+)
β+ (46%)50Fe
51Co272450.97072(16)#60# ms [>200 ns]β+51Fe7/2−#
52Co272551.96359(7)#115(23) msβ+52Fe(6+)
52mCo380(100)# keV104(11)# msβ+52Fe2+#
IT 52Co
53Co272652.954219(19)242(8) msβ+53Fe7/2−#
53mCo3197(29) keV247(12) msβ+ (98.5%)53Fe(19/2−)
p (1.5%)52Fe
54Co272753.9484596(8)193.28(7) msβ+54Fe0+
54mCo197.4(5) keV1.48(2) minβ+54Fe(7)+
55Co272854.9419990(8)17.53(3) hβ+55Fe7/2−
56Co272955.9398393(23)77.233(27) dβ+56Fe4+
57Co273056.9362914(8)271.74(6) d EC 57Fe7/2−
58Co273157.9357528(13)70.86(6) dβ+58Fe2+
58m1Co24.95(6) keV9.04(11) hIT58Co5+
58m2Co53.15(7) keV10.4(3) μs4+
59Co273258.9331950(7)Stable7/2−1.0000
60Co 273359.9338171(7)5.2714(6) yβ−, γ60Ni5+
60mCo58.59(1) keV10.467(6) minIT (99.76%)60Co2+
β− (.24%)60Ni
61Co273460.9324758(10)1.650(5) hβ−61Ni7/2−
62Co273561.934051(21)1.50(4) minβ−62Ni2+
62mCo22(5) keV13.91(5) minβ− (99%)62Ni5+
IT (1%)62Co
63Co273662.933612(21)26.9(4) sβ−63Ni7/2−
64Co273763.935810(21)0.30(3) sβ−64Ni1+
65Co273864.936478(14)1.20(6) sβ−65Ni(7/2)−
66Co273965.93976(27)0.18(1) sβ−66Ni(3+)
66m1Co175(3) keV1.21(1) μs(5+)
66m2Co642(5) keV>100 μs(8-)
67Co274066.94089(34)0.425(20) sβ−67Ni(7/2−)#
68Co274167.94487(34)0.199(21) sβ−68Ni(7-)
68mCo150(150)# keV1.6(3) s(3+)
69Co274268.94632(36)227(13) msβ− (>99.9%)69Ni7/2−#
β−, n (<.1%)68Ni
70Co274369.9510(9)119(6) msβ− (>99.9%)70Ni(6-)
β−, n (<.1%)69Ni
70mCo200(200)# keV500(180) ms(3+)
71Co274470.9529(9)97(2) msβ− (>99.9%)71Ni7/2−#
β−, n (<.1%)70Ni
72Co274571.95781(64)#62(3) msβ− (>99.9%)72Ni(6- ,7-)
β−, n (<.1%)71Ni
73Co274672.96024(75)#41(4) ms7/2−#
74Co274773.96538(86)#50# ms [>300 ns]0+
75Co274874.96833(86)#40# ms [>300 ns]7/2−#
This table header & footer:
  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. 1 2 3 # – 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.

Stellar nucleosynthesis of cobalt-56

One of the terminal nuclear reactions in stars prior to supernova produces 56Ni. Following its production, 56Ni decays to 56Co, and then 56Co subsequently decays to 56Fe. These decay reactions power the luminosity displayed in light decay curves. Both the light decay and radioactive decay curves are expected to be exponential. Therefore, the light decay curve should give an indication of the nuclear reactions powering it. This has been confirmed by observation of bolometric light decay curves for SN 1987A. Between 600 and 800 days after SN1987A occurred, the bolometric light curve decreased at an exponential rate with half-life values from τ1/2 = 68.6 days to τ1/2 = 69.6 days. [5] The rate at which the luminosity decreased closely matched the exponential decay of 56Co with a half-life of τ1/2 = 77.233 days.

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. [6]

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 favor 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. [7] The uses for industrial cobalt include:

57Co 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.

Related Research Articles

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Promethium (61Pm) is an artificial element, except in trace quantities as a product of spontaneous fission of 238U and 235U and alpha decay of 151Eu, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was first synthesized in 1945.

Caesium (55Cs) has 41 known isotopes, the atomic masses of these isotopes range from 112 to 152. Only one isotope, 133Cs, is stable. The longest-lived radioisotopes are 135Cs with a half-life of 1.33 million years, 137
Cs
 with a half-life of 30.1671 years and 134Cs with a half-life of 2.0652 years. All other isotopes have half-lives less than 2 weeks, most under an hour.

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Naturally occurring rhodium (45Rh) is composed of only one stable isotope, 103Rh. The most stable radioisotopes are 101Rh with a half-life of 3.3 years, 102Rh with a half-life of 207 days, and 99Rh with a half-life of 16.1 days. Thirty other radioisotopes have been characterized with atomic weights ranging from 88.949 u (89Rh) to 121.943 u (122Rh). Most of these have half-lives that are less than an hour except 100Rh and 105Rh. There are also numerous meta states with the most stable being 102mRh (0.141 MeV) with a half-life of about 3.7 years and 101mRh (0.157 MeV) with a half-life of 4.34 days.

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Naturally occurring nickel (28Ni) is composed of five stable isotopes; 58
Ni
, 60
Ni
, 61
Ni
, 62
Ni
 and 64
Ni
, with 58
Ni
 being the most abundant. 26 radioisotopes have been characterised with the most stable being 59
Ni
 with a half-life of 76,000 years, 63
Ni
 with a half-life of 100.1 years, and 56
Ni
 with a half-life of 6.077 days. All of the remaining radioactive isotopes have half-lives that are less than 60 hours and the majority of these have half-lives that are less than 30 seconds. This element also has 8 meta states.

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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. "Cobalt-57: Production". JPNM Physics Isotopes. University of Harvard. Archived from the original on 2000-10-31. Retrieved 2013-11-15.
  5. ↑ Bouchet, P.; Danziger, I.J.; Lucy, L.B. (September 1991). "Bolometric Light Curve of SN 1987A: Results from Day 616 to 1316 After Outburst". The Astronomical Journal. 102 (3): 1135–1146 – via Astrophysics Data System.
  6. ↑ Diaz, L. E. "Cobalt-57: Uses". JPNM Physics Isotopes. University of Harvard. Archived from the original on 2011-06-11. Retrieved 2010-09-13.
  7. ↑ "Properties of Cobalt-60". Radioactive Isotopes. Retrieved 2022-12-09.
  8. ↑ "Beneficial Uses of Cobalt-60". INTERNATIONAL IRRADIATION ASSOCIATION. Retrieved 2022-12-09.
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