Berkelium-247

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.

Trace quantities are found in nature from neutron capture by uranium atoms.[1]

Table

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[2][n 1]
daughter
isotope(s)
nuclear
spin
excitation energy
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)E+3 a α 243Am (3/2-)
SF (rare) (various)
248Bk 97 151 248.07309(8)# >9 a 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

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.

See also


References

  • Isotope masses from:
  • Isotopic compositions and standard atomic masses from:
  • Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.


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