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Naturally occurring cobalt, Co, consists of a single stable isotope, Co (thus, cobalt is a mononuclidic element). Twenty-eight radioisotopes have been characterized; the most stable are Co with a half-life of 5.2714 years, Co (271.811 days), Co (77.236 days), and Co (70.844 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 19 meta states, of which the most stable is Co with a half-life of 8.853 h.

The isotopes of cobalt range in atomic weight from Co to Co. The main decay mode for isotopes with atomic mass less than that of the stable isotope, Co, 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 Co are iron isotopes and the main products after are nickel isotopes.

Radioisotopes can be produced by various nuclear reactions. For example, Co is produced by cyclotron irradiation of iron. The main reaction is the (d,n) reaction Fe + H → n + Co.

List of isotopes

1. Co – 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.
8. ^ Order of ground state and isomer is uncertain.

Stellar nucleosynthesis of cobalt-56

One of the terminal nuclear reactions in stars prior to supernova produces Ni. Following its production, Ni decays to Co, and then Co subsequently decays to Fe. 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 τ_1/2 = 68.6 days to τ_1/2 = 69.6 days. The rate at which the luminosity decreased closely matched the exponential decay of Co with a half-life of τ_1/2 = 77.233 days.

Use of cobalt radioisotopes in medicine

Cobalt-57 (Co 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.

Cobalt-60 (Co or Co-60) is used in radiotherapy. It produces two gamma rays with energies of 1.17 MeV and 1.33 MeV. The Co 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 Co 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 (Co) 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. 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

Co is used as a source in Mössbauer spectroscopy of iron-containing samples. Electron capture by Co forms an excited state of the Fe 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. "Cobalt-57: Production". JPNM Physics Isotopes. University of Harvard. Archived from the original on 2000-10-31. Retrieved 2013-11-15.
5. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
6. 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. doi:10.1086/115939 – via Astrophysics Data System.
7. Diaz, L. E. "Cobalt-57: Uses". JPNM Physics Isotopes. University of Harvard. Archived from the original on 2011-06-11. Retrieved 2010-09-13.
8. "Properties of Cobalt-60". Radioactive Isotopes. Retrieved 2022-12-09.
9. "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
• 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.

v t e Isotopes of the chemical elements
Group 1 2   3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Period Hydrogen and alkali metals Alkaline earth metals Pnicto­gens Chal­co­gens Halo­gens Noble gases ① Isotopes § ListH1 Isotopes § ListHe2 ② Isotopes § ListLi3 Isotopes § ListBe4 Isotopes § ListB5 Isotopes § ListC6 Isotopes § ListN7 Isotopes § ListO8 Isotopes § ListF9 Isotopes § ListNe10 ③ Isotopes § ListNa11 Isotopes § ListMg12 Isotopes § ListAl13 Isotopes § ListSi14 Isotopes § ListP15 Isotopes § ListS16 Isotopes § ListCl17 Isotopes § ListAr18 ④ Isotopes § ListK19 Isotopes § ListCa20 Isotopes § ListSc21 Isotopes § ListTi22 Isotopes § ListV23 Isotopes § ListCr24 Isotopes § ListMn25 Isotopes § ListFe26 Isotopes § ListCo27 Isotopes § ListNi28 Isotopes § ListCu29 Isotopes § ListZn30 Isotopes § ListGa31 Isotopes § ListGe32 Isotopes § ListAs33 Isotopes § ListSe34 Isotopes § ListBr35 Isotopes § ListKr36 ⑤ Isotopes § ListRb37 Isotopes § ListSr38 Isotopes § ListY39 Isotopes § ListZr40 Isotopes § ListNb41 Isotopes § ListMo42 Isotopes § ListTc43 Isotopes § ListRu44 Isotopes § ListRh45 Isotopes § ListPd46 Isotopes § ListAg47 Isotopes § ListCd48 Isotopes § ListIn49 Isotopes § ListSn50 Isotopes § ListSb51 Isotopes § ListTe52 Isotopes § ListI53 Isotopes § ListXe54 ⑥ Isotopes § ListCs55 Isotopes § ListBa56 Isotopes § ListLu71 Isotopes § ListHf72 Isotopes § ListTa73 Isotopes § ListW74 Isotopes § ListRe75 Isotopes § ListOs76 Isotopes § ListIr77 Isotopes § ListPt78 Isotopes § ListAu79 Isotopes § ListHg80 Isotopes § ListTl81 Isotopes § ListPb82 Isotopes § ListBi83 Isotopes § ListPo84 Isotopes § ListAt85 Isotopes § ListRn86 ⑦ Isotopes § ListFr87 Isotopes § ListRa88 Isotopes § ListLr103 Isotopes § ListRf104 Isotopes § ListDb105 Isotopes § ListSg106 Isotopes § ListBh107 Isotopes § ListHs108 Isotopes § ListMt109 Isotopes § ListDs110 Isotopes § ListRg111 Isotopes § ListCn112 Isotopes § ListNh113 Isotopes § ListFl114 Isotopes § ListMc115 Isotopes § ListLv116 Isotopes § ListTs117 Isotopes § ListOg118 ⑧ Isotopes § ListUue119 Isotopes § ListUbn120 Isotopes § ListLa57 Isotopes § ListCe58 Isotopes § ListPr59 Isotopes § ListNd60 Isotopes § ListPm61 Isotopes § ListSm62 Isotopes § ListEu63 Isotopes § ListGd64 Isotopes § ListTb65 Isotopes § ListDy66 Isotopes § ListHo67 Isotopes § ListEr68 Isotopes § ListTm69 Isotopes § ListYb70   Isotopes § ListAc89 Isotopes § ListTh90 Isotopes § ListPa91 Isotopes § ListU92 Isotopes § ListNp93 Isotopes § ListPu94 Isotopes § ListAm95 Isotopes § ListCm96 Isotopes § ListBk97 Isotopes § ListCf98 Isotopes § ListEs99 Isotopes § ListFm100 Isotopes § ListMd101 Isotopes § ListNo102
Table of nuclides Categories: Isotopes Tables of nuclides Metastable isotopes Isotopes by element

• Isotopes of cobalt
• Cobalt
• Lists of isotopes by element