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Isotopes of berkelium

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Isotopes of berkelium (97Bk)
Main isotopes Decay
abun­dance half-life (t1/2) mode pro­duct
Bk synth 4.94 d ε Cm
α Am
Bk synth 1.8 d α Am
β Cm
Bk synth 1380 y α Am
Bk synth >9 y α Am
Bk synth 330 d β Cf
α Am
SF

Berkelium (97Bk) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was Bk in 1949. There are twenty known radioisotopes, from Bk and Bk to Bk (except Bk and Bk), and six nuclear isomers. The longest-lived isotope is Bk with a half-life of 1,380 years.

List of isotopes


Nuclide
Z N Isotopic mass (Da)
Half-life
Decay
mode

Daughter
isotope

Spin and
parity
Excitation energy
Bk 97 136 233.05665(25)# 40(30) s α Am 3/2-#
β? Cm
Bk 97 137 234.05732(16)# 20(5) s α (>80%) Am 3-#
β (<20%) Cm
β, SF? (various)
Bk 97 139 236.05748(39)# 26(10) s β (99.96%) Cm 4+#
β, SF (0.04%) (various)
α? Am
Bk 97 141 238.05820(28)# 2.40(8) min β (99.95%) Cm 1#
β, SF (0.048%) (various)
α? Am
Bk 97 142 239.05824(22)# 100# s β Cm (7/2+)
α? Am
SF? (various)
Bk 97 143 240.05976(16)# 4.8(8) min β? Cm 7−#
β, SF (0.0020%) (various)
α? Am
Bk 97 144 241.06010(18)# 4.6(4) min β? Cm (7/2+)
α? Am
Bk 97 145 242.06198(22)# 7.0(13) min β Cm 3+#
β, SF (<3×10%) (various)
α? Am
Bk 2000(200)# keV 600(100) ns SF (various)
IT? Bk
Bk 97 146 243.0630059(49) 4.6(2) h β (99.85%) Cm 3/2−
α (.15%) Am
Bk 97 147 244.065179(15) 5.02(3) h β? Cm 4−
α (0.006%) Am
Bk 1500(500)# keV 820(60) ns SF (various)
IT? Bk
Bk 97 148 245.0663598(19) 4.95(3) d EC (99.88%) Cm 3/2−
α (.12%) Am
Bk 97 149 246.068671(64) 1.80(2) d β Cm 2(−)
α? Am
Bk 97 150 247.0703059(56) 1.38(25)×10 y α Am 3/2−
SF? (various)
Bk 97 151 248.073142(54) >9 y α? Am 6+#
EC? Cm
Bk −20(50) keV 23.7(2) h β (70%) Cf 1(−)
EC (30%) Cm
α? Am
Bk 97 152 249.0749831(13) 327.2(3) d β Cf 7/2+
α (.00145%) Am
SF (4.7×10%) (various)
Bk 8.777(14) keV 300 μs IT Bk 3/2−
Bk 97 153 250.0783172(31) 3.212(5) h β Cf 2−
Bk 35.59(10) keV 29(1) μs IT Bk 4+
Bk 85.6(16) keV 213(8) μs IT Bk 7+
Bk 97 154 251.080761(12) 55.6(11) min β Cf (3/2−)
Bk 35.5(13) keV 58(4) μs IT Bk (7/2+)
Bk 97 155 252.08431(22)# 1.8(5) min β? Cf
α? Am
Bk 97 156 253.08688(39)# 60# min β? Cf 3/2-#
This table header & footer:
  1. Bk – 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. Modes of decay:
    EC: Electron capture
    SF: Spontaneous fission
  5. ( ) spin value – Indicates spin with weak assignment arguments.
  6. ^ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  7. Order of ground state and isomer is uncertain.

Actinides vs fission products

Actinides and fission products by half-life
Actinides by decay chain Half-life
range (a)
Fission products of U by yield
4n 4n + 1 4n + 2 4n + 3 4.5–7% 0.04–1.25% <0.001%
Ra 4–6 a Eu
Bk > 9 a
Cm Pu Cf Ac 10–29 a Sr Kr Cd
U Pu Cm 29–97 a Cs Sm Sn
Cf Am 141–351 a

No fission products have a half-life
in the range of 100 a–210 ka ...

Am Cf 430–900 a
Ra Bk 1.3–1.6 ka
Pu Th Cm Am 4.7–7.4 ka
Cm Cm 8.3–8.5 ka
Pu 24.1 ka
Th Pa 32–76 ka
Np U U 150–250 ka Tc Sn
Cm Pu 327–375 ka Se
1.33 Ma Cs
Np 1.61–6.5 Ma Zr Pd
U Cm 15–24 Ma I
Pu 80 Ma

... nor beyond 15.7 Ma

Th U U 0.7–14.1 Ga

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. Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. doi:10.1016/0029-5582(65)90719-4.
  3. 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.
  4. Kaji, D.; Morimoto, K.; Haba, H.; Ideguchi, E.; Koura, H.; Morita, K. (2016). "Decay Properties of New Isotopes Bk and Am, and Even–Even Nuclides Cm and Pu" (PDF). Journal of the Physical Society of Japan. 84 (15002): 015002. Bibcode:2016JPSJ...85a5002K. doi:10.7566/JPSJ.85.015002.
  5. Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
  6. Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
  7. Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
    "The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk with a half-life greater than 9 . No growth of Cf was detected, and a lower limit for the β half-life can be set at about 10 . No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 ."
  8. This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
  9. Excluding those "classically stable" nuclides with half-lives significantly in excess of Th; e.g., while Cd has a half-life of only fourteen years, that of Cd is eight quadrillion years.
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
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