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Isotopes of cobalt



Naturally occurring cobalt (Co) is composed of 1 stable isotope, 59Co. 22 radioisotopes have been characterized with the most stable being 60Co with a half-life of 5.2714 years, 57Co with a half-life of 271.79 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 4 meta states, all of which have half-lives less than 15 minutes.

The isotopes of cobalt range in atomic weight from 50 u (50Co) to 73 u (73Co). 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 element 26 (iron) isotopes and the primary products after are element 28 (nickel) isotopes.


Standard atomic mass: 58.933195(5) u

Additional recommended knowledge

Contents

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 B-12 uptake. It is useful for the Schilling's test.[1]

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 quantity, and high activity—by simply exposing natural cobalt to neutrons in a reactor for a given time. It is used for

Table

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life 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)# 6+#
49Co 27 22 48.98972(28)# <35 ns 7/2-#
50Co 27 23 49.98154(18)# 44(4) ms (6+)
51Co 27 24 50.97072(16)# 60# ms [>200 ns] 7/2-#
52Co 27 25 51.96359(7)# 115(23) ms (6+)
52mCo 380(100)# keV 104(11)# ms 2+#
53Co 27 26 52.954219(19) 242(8) ms 7/2-#
53mCo 3197(29) keV 247(12) ms (19/2-)
54Co 27 27 53.9484596(8) 193.28(7) ms 0+
54mCo 197.4(5) keV 1.48(2) min (7)+
55Co 27 28 54.9419990(8) 17.53(3) h 7/2-
56Co 27 29 55.9398393(23) 77.233(27) d 4+
57Co 27 30 56.9362914(8) 271.74(6) d 7/2-
58Co 27 31 57.9357528(13) 70.86(6) d 2+
58m1Co 24.95(6) keV 9.04(11) h 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) a 5+
60mCo 58.59(1) keV 10.467(6) min 2+
61Co 27 34 60.9324758(10) 1.650(5) h 7/2-
62Co 27 35 61.934051(21) 1.50(4) min 2+
62mCo 22(5) keV 13.91(5) min 5+
63Co 27 36 62.933612(21) 26.9(4) s 7/2-
64Co 27 37 63.935810(21) 0.30(3) s 1+
65Co 27 38 64.936478(14) 1.20(6) s (7/2)-
66Co 27 39 65.93976(27) 0.18(1) s (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 (7/2-)#
68Co 27 41 67.94487(34) 0.199(21) s (7-)
68mCo 150(150)# keV 1.6(3) s (3+)
69Co 27 42 68.94632(36) 227(13) ms 7/2-#
70Co 27 43 69.9510(9) 119(6) ms (6-)
70mCo 200(200)# keV 500(180) ms (3+)
71Co 27 44 70.9529(9) 97(2) ms 7/2-#
72Co 27 45 71.95781(64)# 62(3) ms (6-,7-)
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.

Table 2

Cobalt Isotopes[2]
Isotope Decay mechanism Half life
Co-50 positron emission 44 millisecond
Co-51 positron emission unmeasured
Co-52 positron emission 0.12 second
Co-53 positron emission 0.24 second
Co-54 positron emission 193.2 millisecond
Co-55 positron emission 17.53 h
Co-56 electron capture, positron emission 77.3 d
Co-57 positron emission 271.8 d
Co-58 electron capture 70.88 d
Co-59 stable
Co-60 beta decay 5.271 yr
Co-61 beta decay 1.65 hr
Co-62 beta decay 1.5 min
Co-63 beta decay 27.5 second
Co-64 beta decay 0.30 second
Co-65 beta decay 1.17 second
Co-66 beta decay 0.190 second
Co-67 beta decay 0.43 second
Co-68 beta decay 0.20 second
Co-69 beta decay 0.22 second
Co-70 beta decay 0.13 second
Co-71 beta decay 0.21 second
Co-72 beta decay 90 millisecond

References

  1. ^ JPNM Physics Isotopes
  2. ^ Nuclides and Isotopes: Chart of the Nuclides, 16th Edition, by Edward Baum, Harold Knox, and Thomas Miller; Knolls Atomic Power Laboratory; 2002
  • Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
  • Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
  • Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
    • Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
    • National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
    • 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
Index to isotope pages
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Isotopes_of_cobalt". A list of authors is available in Wikipedia.
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