# Isotopes of berkelium

Berkelium ($_{97}$Bk) 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 $^{243}$Bk in 1949. There are twenty known radioisotopes, from $^{233}$Bk and $^{233}$Bk to $^{253}$Bk (except $^{235}$Bk and $^{237}$Bk), and six nuclear isomers. The longest-lived isotope is $^{247}$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 |
| Spin and parity |||
| $^{233}$Bk | 97 | 136 | 233.05665(25)# | 40(30) s | α | $^{229}$Am | 3/2-# |
| $^{233}$Bk | 97 | 136 | 233.05665(25)# | 40(30) s | β$^+$? | $^{233}$Cm | 3/2-# |
| $^{234}$Bk | 97 | 137 | 234.05732(16)# | 20(5) s | α (>80%) | $^{230}$Am | 3-# |
| $^{234}$Bk | 97 | 137 | 234.05732(16)# | 20(5) s | β$^+$ (<20%) | $^{234}$Cm | 3-# |
| $^{234}$Bk | 97 | 137 | 234.05732(16)# | 20(5) s | β$^+$, SF? | (various) | 3-# |
| $^{236}$Bk | 97 | 139 | 236.05748(39)# | 26(10) s | β$^+$ (99.96%) | $^{236}$Cm | 4+# |
| $^{236}$Bk | 97 | 139 | 236.05748(39)# | 26(10) s | β$^+$, SF (0.04%) | (various) | 4+# |
| $^{236}$Bk | 97 | 139 | 236.05748(39)# | 26(10) s | α? | $^{232}$Am |
| $^{238}$Bk | 97 | 141 | 238.05820(28)# | 2.40(8) min | β$^+$ (99.95%) | $^{238}$Cm | 1# |
| $^{238}$Bk | 97 | 141 | 238.05820(28)# | 2.40(8) min | β$^+$, SF (0.048%) | (various) | 1# |
| $^{238}$Bk | 97 | 141 | 238.05820(28)# | 2.40(8) min | α? | $^{234}$Am | 1# |
| $^{239}$Bk | 97 | 142 | 239.05824(22)# | 100# s | β$^+$ | $^{239}$Cm | (7/2+) |
| $^{239}$Bk | 97 | 142 | 239.05824(22)# | 100# s | α? | $^{235}$Am | (7/2+) |
| $^{239}$Bk | 97 | 142 | 239.05824(22)# | 100# s | SF? | (various) | (7/2+) |
| $^{240}$Bk | 97 | 143 | 240.05976(16)# | 4.8(8) min | β$^+$? | $^{240}$Cm | 7−# |
| $^{240}$Bk | 97 | 143 | 240.05976(16)# | 4.8(8) min | β$^+$, SF (0.0020%) | (various) | 7−# |
| $^{240}$Bk | 97 | 143 | 240.05976(16)# | 4.8(8) min | α? | $^{236}$Am | 7−# |
| $^{241}$Bk | 97 | 144 | 241.06010(18)# | 4.6(4) min | β$^+$? | $^{241}$Cm | (7/2+) |
| $^{241}$Bk | 97 | 144 | 241.06010(18)# | 4.6(4) min | α? | $^{237}$Am | (7/2+) |
| $^{242}$Bk | 97 | 145 | 242.06198(22)# | 7.0(13) min | β$^+$ | $^{242}$Cm | 3+# |
| $^{242}$Bk | 97 | 145 | 242.06198(22)# | 7.0(13) min | β$^+$, SF (<3×10$^{−5}$%) | (various) | 3+# |
| $^{242}$Bk | 97 | 145 | 242.06198(22)# | 7.0(13) min | α? | $^{238}$Am | 3+# |
| $^{242m}$Bk | 2000(200)# keV | 2000(200)# keV | 2000(200)# keV | 600(100) ns | SF | (various) | |
| $^{242m}$Bk | 2000(200)# keV | 2000(200)# keV | 2000(200)# keV | 600(100) ns | IT? | $^{242}$Bk | |
| $^{243}$Bk | 97 | 146 | 243.0630059(49) | 4.6(2) h | β$^+$ (99.85%) | $^{243}$Cm | 3/2− |
| $^{243}$Bk | 97 | 146 | 243.0630059(49) | 4.6(2) h | α (.15%) | $^{239}$Am | 3/2− |
| $^{244}$Bk | 97 | 147 | 244.065179(15) | 5.02(3) h | β$^+$? | $^{244}$Cm | 4− |
| $^{244}$Bk | 97 | 147 | 244.065179(15) | 5.02(3) h | α (0.006%) | $^{240}$Am | 4− |
| $^{244m}$Bk | 1500(500)# keV | 1500(500)# keV | 1500(500)# keV | 820(60) ns | SF | (various) | |
| $^{244m}$Bk | 1500(500)# keV | 1500(500)# keV | 1500(500)# keV | 820(60) ns | IT? | $^{244}$Bk | |
| $^{245}$Bk | 97 | 148 | 245.0663598(19) | 4.95(3) d | EC (99.88%) | $^{245}$Cm | 3/2− |
| $^{245}$Bk | 97 | 148 | 245.0663598(19) | 4.95(3) d | α (.12%) | $^{241}$Am | 3/2− |
| $^{246}$Bk | 97 | 149 | 246.068671(64) | 1.80(2) d | β$^+$ | $^{246}$Cm | 2(−) |
| $^{246}$Bk | 97 | 149 | 246.068671(64) | 1.80(2) d | α? | $^{242}$Am | 2(−) |
| $^{247}$Bk | 97 | 150 | 247.0703059(56) | 1.38(25)×10$^3$ y | α | $^{243}$Am | 3/2− |
| $^{247}$Bk | 97 | 150 | 247.0703059(56) | 1.38(25)×10$^3$ y | SF? | (various) | 3/2− |
| $^{248}$Bk | 97 | 151 | 248.073142(54) | >9 y | α? | $^{244}$Am | 6+# |
| $^{248}$Bk | 97 | 151 | 248.073142(54) | >9 y | EC? | $^{248}$Cm | 6+# |
| $^{248m}$Bk | −20(50) keV | −20(50) keV | −20(50) keV | 23.7(2) h | β$^−$ (70%) | $^{248}$Cf | 1(−) |
| $^{248m}$Bk | −20(50) keV | −20(50) keV | −20(50) keV | 23.7(2) h | EC (30%) | $^{248}$Cm | 1(−) |
| $^{248m}$Bk | −20(50) keV | −20(50) keV | −20(50) keV | 23.7(2) h | α? | $^{244}$Am | 1(−) |
| $^{249}$Bk | 97 | 152 | 249.0749831(13) | 327.2(3) d | β$^−$ | $^{249}$Cf | 7/2+ |
| $^{249}$Bk | 97 | 152 | 249.0749831(13) | 327.2(3) d | α (.00145%) | $^{245}$Am | 7/2+ |
| $^{249}$Bk | 97 | 152 | 249.0749831(13) | 327.2(3) d | SF (4.7×10$^{−8}$%) | (various) | 7/2+ |
| $^{249m}$Bk | 8.777(14) keV | 8.777(14) keV | 8.777(14) keV | 300 μs | IT | $^{249}$Bk | 3/2− |
| $^{250}$Bk | 97 | 153 | 250.0783172(31) | 3.212(5) h | β$^−$ | $^{250}$Cf | 2− |
| $^{250m1}$Bk | 35.59(10) keV | 35.59(10) keV | 35.59(10) keV | 29(1) μs | IT | $^{250}$Bk | 4+ |
| $^{250m2}$Bk | 85.6(16) keV | 85.6(16) keV | 85.6(16) keV | 213(8) μs | IT | $^{250}$Bk | 7+ |
| $^{251}$Bk | 97 | 154 | 251.080761(12) | 55.6(11) min | β$^−$ | $^{251}$Cf | (3/2−) |
| $^{251m}$Bk | 35.5(13) keV | 35.5(13) keV | 35.5(13) keV | 58(4) μs | IT | $^{251}$Bk | (7/2+) |
| $^{252}$Bk | 97 | 155 | 252.08431(22)# | 1.8(5) min | β$^−$? | $^{252}$Cf | |
| $^{252}$Bk | 97 | 155 | 252.08431(22)# | 1.8(5) min | α? | $^{248}$Am | |
| $^{253}$Bk | 97 | 156 | 253.08688(39)# | 60# min | β$^−$? | $^{253}$Cf | 3/2-# |
| This table header & footer: view ||||||||
* ↑ $^m$Bk – Excited nuclear isomer.
* ↑ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
* ↑ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
* ↑ Modes of decay: EC:Electron capture SF:Spontaneous fission
* ↑ ( ) spin value – Indicates spin with weak assignment arguments.
* 1 2 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
* ↑ Order of ground state and isomer is uncertain.

## Actinides vs fission products

Actinides and fission products by half-life vte :
| Actinides by decay chain | Actinides by decay chain | Actinides by decay chain | Actinides by decay chain | Half-life range (a) | Fission products of $^{235}$U by yield | Fission products of $^{235}$U by yield | Fission products of $^{235}$U by yield |
| 4n | 4n + 1 | 4n + 2 | 4n + 3 | Half-life range (a) | 4.5–7% | 0.04–1.25% | <0.001% |
| Ra$^№$ | | | | 4–6 a | | Eu$^þ$ | |
| Bk | | | | > 9 a | | | |
| Cm$^ƒ$ | Pu$^ƒ$ | Cf | Ac$^№$ | 10–29 a | Sr | Kr | Cd$^þ$ |
| U$^ƒ$ | | Pu$^ƒ$ | Cm$^ƒ$ | 29–97 a | Cs | Sm$^þ$ | Sn |
| | Cf$^ƒ$ | Am$^ƒ$ | | 141–351 a | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | Am$^ƒ$ | | Cf$^ƒ$ | 430–900 a | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | | Ra$^№$ | Bk | 1.3–1.6 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| Pu | Th | Cm$^ƒ$ | Am$^ƒ$ | 4.7–7.4 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | Cm$^ƒ$ | Cm | | 8.3–8.5 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | | | Pu$^ƒ$ | 24.1 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | | Th$^№$ | Pa$^№$ | 32–76 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| Np$^ƒ$ | U$^ƒ$ | U$^№$ | | 150–250 ka | Tc$^₡$ | Sn |
| Cm | | Pu | | 327–375 ka | | Se$^₡$ |
| | | | | 1.33 Ma | Cs$^₡$ |
| | Np$^ƒ$ | | | 1.61–6.5 Ma | Zr | Pd |
| U | | | Cm$^ƒ$ | 15–24 Ma | | I$^₡$ |
| Pu | | | | 80 Ma | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma |
| Th$^№$ | | U$^№$ | U$^{ƒ№}$ | 0.7–14.1 Ga | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma |
| ₡, has thermal neutron capture cross section in the range of 8–50 barnsƒ, fissile№, primarily a naturally occurring radioactive material (NORM)þ, neutron poison (thermal neutron capture cross section greater than 3k barns) |||||||||