Isotopes of berkelium

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 ²⁴³Bk in 1949. There are twenty known radioisotopes, from ²³³Bk and ²³³Bk to ²⁵³Bk (except ²³⁵Bk and ²³⁷Bk), and six nuclear isomers. The longest-lived isotope is ²⁴⁷Bk with a half-life of 1,380 years.

Isotopes of berkelium (₉₇Bk)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 245Bk synth 4.94 d ε 245Cm α 241Am 246Bk synth 1.8 d α 242Am β+ 246Cm 247Bk synth 1380 y α 243Am 248Bk synth >9 y[2] α 244Am 249Bk synth 330 d β− 249Cf α 245Am SF –

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List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da)[3] [n 2][n 3]	Half-life[1]	Decay mode[1] [n 4]	Daughter isotope	Spin and parity[1] [n 5][n 6]
	Excitation energy[n 6]
233Bk	97	136	233.05665(25)#	40(30) s	α	229Am	3/2-#
					β+?	233Cm
234Bk	97	137	234.05732(16)#	20(5) s	α (>80%)	230Am	3-#
					β+ (<20%)	234Cm
					β+, SF?[4]	(various)
236Bk	97	139	236.05748(39)#	26(10) s	β+ (99.96%)	236Cm	4+#
					β+, SF (0.04%)	(various)
					α?	232Am
238Bk	97	141	238.05820(28)#	2.40(8) min	β+ (99.95%)	238Cm	1#
					β+, SF (0.048%)	(various)
					α?	234Am
239Bk	97	142	239.05824(22)#	100# s	β+	239Cm	(7/2+)
					α?	235Am
					SF?	(various)
240Bk	97	143	240.05976(16)#	4.8(8) min	β+?	240Cm	7−#
					β+, SF (0.0020%)	(various)
					α?	236Am
241Bk	97	144	241.06010(18)#	4.6(4) min	β+?	241Cm	(7/2+)
					α?	237Am
242Bk	97	145	242.06198(22)#	7.0(13) min	β+	242Cm	3+#
					β+, SF (<3×10−5%)	(various)
					α?	238Am
242mBk	2000(200)# keV			600(100) ns	SF	(various)
					IT?	242Bk
243Bk	97	146	243.0630059(49)	4.6(2) h	β+ (99.85%)	243Cm	3/2−
					α (.15%)	239Am
244Bk	97	147	244.065179(15)	5.02(3) h	β+?	244Cm	4−
					α (0.006%)	240Am
244mBk	1500(500)# keV			820(60) ns	SF	(various)
					IT?	244Bk
245Bk	97	148	245.0663598(19)	4.95(3) d	EC (99.88%)	245Cm	3/2−
					α (.12%)	241Am
246Bk	97	149	246.068671(64)	1.80(2) d	β+	246Cm	2(−)
					α?	242Am
247Bk	97	150	247.0703059(56)	1.38(25)×103 y	α	243Am	3/2−
					SF?	(various)
248Bk	97	151	248.073142(54)	>9 y	α?	244Am	6+#
					EC?	248Cm
248mBk	−20(50) keV[n 7]			23.7(2) h	β− (70%)	248Cf	1(−)
					EC (30%)	248Cm
					α?	244Am
249Bk	97	152	249.0749831(13)	327.2(3) d	β−	249Cf	7/2+
					α (.00145%)	245Am
					SF (4.7×10−8%)	(various)
249mBk	8.777(14) keV			300 μs	IT	249Bk	3/2−
250Bk	97	153	250.0783172(31)	3.212(5) h	β−	250Cf	2−
250m1Bk	35.59(10) keV			29(1) μs	IT	250Bk	4+
250m2Bk	85.6(16) keV			213(8) μs	IT	250Bk	7+
251Bk	97	154	251.080761(12)	55.6(11) min	β−	251Cf	(3/2−)
251mBk	35.5(13) keV			58(4) μs	IT	251Bk	(7/2+)
252Bk	97	155	252.08431(22)#	1.8(5) min	β−?	252Cf
					α?	248Am
253Bk	97	156	253.08688(39)#	60# min	β−?	253Cf	3/2-#
This table header & footer: view

1. ^mBk – 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.^[1][5]

Actinides vs fission products

Actinides and fission products by half-life v t e
Actinides[6] by decay chain				Half-life range (a)	Fission products of 235U by yield[7]
4n	4n + 1	4n + 2	4n + 3		4.5–7%	0.04–1.25%	<0.001%
228Ra№				4–6 a		155Euþ
248Bk[8]				> 9 a
244Cmƒ	241Puƒ	250Cf	227Ac№	10–29 a	90Sr	85Kr	113mCdþ
232Uƒ		238Puƒ	243Cmƒ	29–97 a	137Cs	151Smþ	121mSn
	249Cfƒ	242mAmƒ		141–351 a	No fission products have a half-life in the range of 100 a–210 ka ...
	241Amƒ		251Cfƒ[9]	430–900 a
		226Ra№	247Bk	1.3–1.6 ka
240Pu	229Th	246Cmƒ	243Amƒ	4.7–7.4 ka
	245Cmƒ	250Cm		8.3–8.5 ka
			239Puƒ	24.1 ka
		230Th№	231Pa№	32–76 ka
236Npƒ	233Uƒ	234U№		150–250 ka	99Tc₡	126Sn
248Cm		242Pu		327–375 ka		79Se₡
				1.33 Ma	135Cs₡
	237Npƒ			1.61–6.5 Ma	93Zr	107Pd
236U			247Cmƒ	15–24 Ma		129I₡
244Pu				80 Ma	... nor beyond 15.7 Ma[10]
232Th№		238U№	235Uƒ№	0.7–14.1 Ga
₡,  has thermal neutron capture cross section in the range of 8–50 barns ƒ,  fissile №,  primarily a naturally occurring radioactive material (NORM) þ,  neutron poison (thermal neutron capture cross section greater than 3k barns)

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 ²³⁴Bk and ²³⁰Am, and Even–Even Nuclides ²³⁴Cm and ²³⁰Pu" (PDF). Journal of the Physical Society of Japan. 84 (15002): 015002. Bibcode:2016JPSJ...85a5002K. doi:10.7566/JPSJ.85.015002.
5. "Adopted Levels for ²⁴⁸Bk". NNDC Chart of Nuclides.
6. 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.
7. Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
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. 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 Bk²⁴⁸ with a half-life greater than 9 [years]. No growth of Cf²⁴⁸ was detected, and a lower limit for the β⁻ half-life can be set at about 10⁴ [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]."
9. This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
10. Excluding those "classically stable" nuclides with half-lives significantly in excess of ²³²Th; e.g., while ^113mCd has a half-life of only fourteen years, that of ¹¹³Cd is eight quadrillion years.

• Isotope masses from:
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.