Isotopes of berkelium

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 1.80 d β+ 246Cm α 242Am 247Bk synth 1380 y α 243Am 248Bk synth >9 y [2] α 244Am 249Bk synth 327.2 d β− 249Cf α 245Am SF –

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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 nineteen known radioisotopes, from ²³³Bk to ²⁵³Bk (except ²³⁵Bk and ²³⁷Bk), and seven nuclear isomers. The longest-lived isotope known is ²⁴⁷Bk with a half-life of 1,380 years; however ²⁴⁸Bk, which has not been observed to decay, may live longer.

The isotope commonly used in study, though, is ²⁴⁹Bk as is it the only that can be usefully extracted from reactor actinides and the only ever available in weighable quantity.

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 (82%)	229Am	3/2−#
					β+? (18%)	233Cm
234Bk	97	137	234.05732(16)#	20(5) s	α (>80%)	230Am	3−#
					β+ (<20%)	234Cm
236Bk	97	139	236.05748(39)#	26(10) s	β+ (99.96%)	236Cm	4+#
					β+, SF (0.04%)	(various)
238Bk	97	141	238.05820(28)#	2.40(8) min	β+ (99.95%)	238Cm	1#
					β+, SF (0.048%)	(various)
239Bk	97	142	239.05824(22)#	100# s	β+	239Cm	(7/2+)
240Bk	97	143	240.05976(16)#	4.8(8) min	β+?	240Cm	7−#
					α?	236Am
					β+, SF (0.0013%)	(various)
241Bk	97	144	241.06010(18)#	4.6(4) min	β+	241Cm	(7/2+)
242Bk	97	145	242.06200(14)#	7.0(13) min	β+	242Cm	3+#
					β+, SF (<3×10−5%)	(various)
242mBk	2000(200)# keV			600(100) ns	SF	(various)
243Bk	97	146	243.063006(5)	4.6(2) h	β+ (99.85%)	243Cm	3/2−
					α (0.15%)	239Am
244Bk	97	147	244.065179(15)	5.02(3) h	β+ (99.994%) [n 7]	244Cm	4−
					α (0.006%)	240Am
244mBk	1500(500)# keV			820(60) ns	SF	(various)
245Bk	97	148	245.0663598(19)	4.95(3) d	EC (99.88%)	245Cm	3/2−
					α (0.12%)	241Am
246Bk	97	149	246.06867(6)	1.80(2) d	β+	246Cm	2(−)
247Bk	97	150	247.070306(6)	1.38(25)×103 y	α	243Am	3/2−
					SF?	(various)
248Bk	97	151	248.07314(5)	>9 y	α?	244Am	6+#
					EC?	248Cm
					β−?	248Cf
248mBk [n 8]	−20(50) keV			23.7(2) h	β− (70%)	248Cf	1(−)
					EC (30%)	248Cm
249Bk [n 9]	97	152	249.0749831(13)	327.2(3) d	β−	249Cf	7/2+
					α (0.00145%)	245Am
					SF (4.7×10−8%)	(various)
249mBk	8.777(14) keV			300 μs	IT	249Bk	3/2−
250Bk	97	153	250.078317(3)	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
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. NUBASE2020 question-marks this decay, but it has been observed directly, see e.g. the IAEA Chart of Nuclides.
8. Order of ground state and isomer is uncertain.
9. Most common isotope

Actinides vs fission products

Actinides and fission products by half-life v t e
Actinides [4] by decay chain				Half-life range (a)	Fission products of 235U by yield [5]
4n	4n + 1	4n + 2	4n + 3		4.5–7%	0.04–1.25%	<0.001%
228 Ra№				4–6 a		155 Euþ
248 Bk [6]				> 9 a
244 Cmƒ	241 Puƒ	250 Cf	227 Ac№	10–29 a	90 Sr	85 Kr	113m Cdþ
232 Uƒ		238 Puƒ	243 Cmƒ	29–97 a	137 Cs	151 Smþ	121m Sn
	249 Cfƒ	242m Amƒ		141–351 a	No fission products have a half-life in the range of 100 a–210 ka ...
	241 Amƒ		251 Cfƒ [7]	430–900 a
		226 Ra№	247 Bk	1.3–1.6 ka
240 Pu	229 Th	246 Cmƒ	243 Amƒ	4.7–7.4 ka
	245 Cmƒ	250 Cm		8.3–8.5 ka
			239 Puƒ	24.1 ka
		230 Th№	231 Pa№	32–76 ka
236 Npƒ	233 Uƒ	234 U№		150–250 ka	99 Tc₡	126 Sn
248 Cm		242 Pu		327–375 ka		79 Se₡
				1.33 Ma	135 Cs₡
	237 Npƒ			1.61–6.5 Ma	93 Zr	107 Pd
236 U			247 Cmƒ	15–24 Ma		129 I₡
244 Pu				80 Ma	... nor beyond 15.7 Ma [8]
232 Th№		238 U№	235 Uƒ№	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. 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.
5. Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
6. 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]."
7. This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
8. 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 3.0 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.