Isotopes of berkelium

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Actinides and fission products by half-life
Actinides[1] by decay chain Half-life
range (y)
Fission products of 235U by yield[2]
4n 4n+1 4n+2 4n+3
4.5–7% 0.04–1.25% <0.001%
228Ra 4–6 155Euþ
244Cmƒ 241Puƒ 250Cf 227Ac 10–29 90Sr 85Kr 113mCdþ
232Uƒ 238Puƒ№ 243Cmƒ 29–97 137Cs 151Smþ 121mSn
248Bk[3] 249Cfƒ 242mAmƒ 141–351

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

241Amƒ 251Cfƒ[4] 430–900
226Ra 247Bk 1.3 k – 1.6 k
240Puƒ№ 229Th 246Cmƒ 243Amƒ 4.7 k – 7.4 k
245Cmƒ 250Cm 8.3 k – 8.5 k
239Puƒ№ 24.1 k
230Th 231Pa 32 k – 76 k
236Npƒ 233Uƒ№ 234U 150 k – 250 k 99Tc 126Sn
248Cm 242Puƒ 327 k – 375 k 79Se
1.53 M 93Zr
237Npƒ№ 2.1 M – 6.5 M 135Cs 107Pd
236U 247Cmƒ 15 M – 24 M 129I
244Pu 80 M

... nor beyond 15.7 M years[5]

232Th 238U 235Uƒ№ 0.7 G – 14.1 G

Legend for superscript symbols
₡  has thermal neutron capture cross section in the range of 8–50 barns
ƒ  fissile
metastable isomer
№  naturally occurring radioactive material (NORM)
þ  neutron poison (thermal neutron capture cross section greater than 3k barns)
†  range 4–97 y: Medium-lived fission product
‡  over 200,000 y: Long-lived fission product

Berkelium (Bk) is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 243Bk in 1949. There are 20 known radioisotopes, from 235Bk to 254Bk, and 6 nuclear isomers. The longest-lived isotope is 247Bk with a half-life of 1,380 years.

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[6][n 1]
daughter
isotope(s)
nuclear
spin
excitation energy
233Bk[7] 97 136 21 s α 229Am
235Bk 97 138 235.05658(43)# 20# s α 231Am
β+ 235Cm
236Bk 97 139 236.05733(43)# 1# min α 232Am
β+ 236Cm
237Bk 97 140 237.05700(24)# 1# min α 233Am 7/2+#
β+ (rare) 237Cm
238Bk 97 141 238.05828(31)# 2.40(8) min α 234Am
β+, SF (.048%) (various)
β+ (rare) 238Cm
239Bk 97 142 239.05828(25)# 3# min α 235Am 7/2+#
β+ 239Cm
240Bk 97 143 240.05976(16)# 4.8(8) min β+ (90%) 240Cm
α (10%) 236Am
β+, SF (.002%) (various)
241Bk 97 144 241.06023(22)# 4.6(4) min α 237Am (7/2+)
β+ (rare) 241Cm
242Bk 97 145 242.06198(22)# 7.0(13) min β+ (99.99%) 242Cm 2−#
β+, SF (3×10−4%) (various)
242mBk 200(200)# keV 600(100) ns
243Bk 97 146 243.063008(5) 4.5(2) h β+ (99.85%) 243Cm (3/2−)
α (.15%) 239Am
244Bk 97 147 244.065181(16) 4.35(15) h β+ (99.99%) 244Cm (4−)#
α (.006%) 240Am
245Bk 97 148 245.0663616(25) 4.94(3) d EC (99.88%) 245Cm 3/2−
α (.12%) 241Am
246Bk 97 149 246.06867(6) 1.80(2) d β+ (99.8%) 246Cm 2(−)
α (.2%) 242Am
247Bk 97 150 247.070307(6) 1.38(25)×103 y α 243Am (3/2−)
SF (rare) (various)
248Bk 97 151 248.07309(8)# >300 y[8] α 244Am 6+#
248mBk 30(70)# keV 23.7(2) h 1(−)
249Bk[n 2] 97 152 249.0749867(28) 330(4) d β 249Cf 7/2+
α (.00145%) 245Am
SF (4.7×10−8%) (various)
249mBk 8.80(10) keV 300 µs (3/2−)
250Bk 97 153 250.078317(4) 3.212(5) h β 250Cf 2−
250m1Bk 35.59(5) keV 29(1) µs (4+)
250m2Bk 84.1(21) keV 213(8) µs (7+)
251Bk 97 154 251.080760(12) 55.6(11) min β 251Cf (3/2−)#
α (10−5%) 247Am
251mBk 35.5(13) keV 58(4) µs (7/2+)#
252Bk 97 155 252.08431(22)# 1.8(5) min β 252Cf
α 248Am
253Bk 97 156 253.08688(39)# 10# min β 253Cf
254Bk 97 157 254.09060(32)# 1# min β 254Cf
  1. ^ Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
    SF: Spontaneous fission
  2. ^ Easiest isotope to synthesize

Notes[edit]

  • 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.

See also[edit]

References[edit]

  1. ^ 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 isotopes have half-lives of at least four years (the longest-lived isotope 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.
  2. ^ Specifically from thermal neutron fission of U-235, e.g. in a typical nuclear reactor.
  3. ^ 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. 
    "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 Bk248 with a half-life greater than 9 y. No growth of Cf248 was detected, and a lower limit for the β half-life can be set at about 104 y. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 y."
  4. ^ This is the heaviest isotope with a half-life of at least four years before the "Sea of Instability".
  5. ^ Excluding those "classically stable" isotopes with half-lives significantly in excess of 232Th; e.g., while 113mCd has a half-life of only fourteen years, that of 113Cd is nearly eight quadrillion years.
  6. ^ "Universal Nuclide Chart". nucleonica. (registration required (help)). 
  7. ^ "Observation of new neutron-deficient isotopes with Z ≥ 92 in multinucleon transfer reactions" http://inspirehep.net/record/1383747/files/scoap3-fulltext.pdf
  8. ^ 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. 


Isotopes of curium Isotopes of berkelium Isotopes of californium
Table of nuclides