Isotopes of curium

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		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	†		¹⁵⁵Eu^þ
²⁴⁴Cm	²⁴¹Pu^ƒ	²⁵⁰Cf	²²⁷Ac^№	10–29		⁹⁰Sr	⁸⁵Kr	^113mCd^þ
²³²U^ƒ		²³⁸Pu^№	²⁴³Cm^ƒ	29–97		¹³⁷Cs	¹⁵¹Sm^þ	^121mSn
²⁴⁸Bk^[3]	²⁴⁹Cf^ƒ	^242mAm^ƒ		141–351	No fission products have a half-life in the range of 100–210 k years ...
	²⁴¹Am^ƒ		²⁵¹Cf^ƒ^[4]	430–900
		²²⁶Ra^№	²⁴⁷Bk	1.3 k – 1.6 k
²⁴⁰Pu	²²⁹Th^№	²⁴⁶Cm	²⁴³Am^ƒ	4.7 k – 7.4 k
	²⁴⁵Cm^ƒ	²⁵⁰Cm		8.3 k – 8.5 k
			²³⁹Pu^ƒ№	24.1 k
		²³⁰Th^№	²³¹Pa^№	32 k – 76 k
²³⁶Np^ƒ	²³³U^ƒ№	²³⁴U^№		150 k – 250 k	‡	⁹⁹Tc^₡	¹²⁶Sn
²⁴⁸Cm		²⁴²Pu		327 k – 375 k			⁷⁹Se^₡
				1.53 M		⁹³Zr
	²³⁷Np^№			2.1 M – 6.5 M		¹³⁵Cs^₡	¹⁰⁷Pd
²³⁶U^№			²⁴⁷Cm^ƒ	15 M – 24 M			¹²⁹I^₡
²⁴⁴Pu^№				80 M	... nor beyond 15.7 M years^[5]
²³²Th^№		²³⁸U^№	²³⁵U^ƒ№	0.7 G – 14.1 G	... nor beyond 15.7 M years^[5]
Legend for superscript symbols ₡ has thermal neutron capture cross section in the range of 8–50 barns ƒ fissile m 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

Curium (Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic mass cannot be given, and it has no stable isotopes. The first isotope synthesized was ²⁴²Cm in 1944, which has 146 neutrons. All of the isotopes are radioactive.

There are 21 known radioisotopes with atomic masses ranging from ²³²Cm to ²⁵²Cm. There are also four known nuclear isomers (^243mCm, ^244mCm, ^245mCm, and ^249mCm). The longest-lived isotope is ²⁴⁷Cm, with a half-life of 15.6 million years – several orders of magnitude longer than the half-life of all known nuclei of elements beyond curium in the periodic table. The longest-lived isomer is ^244mCm with a half-life of 34 milliseconds.

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)^[6]^{[n 1]}	daughter isotope(s)^{[n 2]}	nuclear spin
nuclide symbol	excitation energy			half-life	decay mode(s)^[6]^{[n 1]}	daughter isotope(s)^{[n 2]}	nuclear spin
²³²Cm	96	136		1? min			0+
²³³Cm	96	137	233.05077(8)	1# min	β⁺	²³³Am	3/2+#
²³³Cm	96	137	233.05077(8)	1# min	α	²²⁹Pu	3/2+#
²³⁴Cm	96	138	234.05016(2)	51(12) s	β⁺	²³⁴Am	0+
²³⁴Cm	96	138	234.05016(2)	51(12) s	α	²³⁰Pu	0+
²³⁵Cm	96	139	235.05143(22)#	5# min	β⁺	²³⁵Am	5/2+#
²³⁵Cm	96	139	235.05143(22)#	5# min	α	²³¹Pu	5/2+#
²³⁶Cm	96	140	236.05141(22)#	10# min	β⁺	²³⁶Am	0+
²³⁶Cm	96	140	236.05141(22)#	10# min	α	²³²Pu	0+
²³⁷Cm	96	141	237.05290(22)#	20# min	β⁺	²³⁷Am	5/2+#
²³⁷Cm	96	141	237.05290(22)#	20# min	α	²³³Pu	5/2+#
²³⁸Cm	96	142	238.05303(4)	2.4(1) h	EC (90%)	²³⁸Am	0+
²³⁸Cm	96	142	238.05303(4)	2.4(1) h	α (10%)	²³⁴Pu	0+
²³⁹Cm	96	143	239.05496(11)#	~2.9 h	β⁺ (99.9%)	²³⁹Am	(7/2−)
²³⁹Cm	96	143	239.05496(11)#	~2.9 h	α (.1%)	²³⁵Pu	(7/2−)
²⁴⁰Cm	96	144	240.0555295(25)	27(1) d	α (99.5%)	²³⁶Pu	0+
					EC (.5%)	²⁴⁰Am
					SF (3.9×10⁻⁶%)	(various)
²⁴¹Cm	96	145	241.0576530(23)	32.8(2) d	EC (99%)	²⁴¹Am	1/2+
²⁴¹Cm	96	145	241.0576530(23)	32.8(2) d	α (1%)	²³⁷Pu	1/2+
²⁴²Cm^{[n 3]}	96	146	242.0588358(20)	162.8(2) d	α	²³⁸Pu	0+
					SF (6.33×10⁻⁶%)	(various)
					CD (10⁻¹⁴%)^{[n 4]}	²⁰⁸Pb ³⁴Si
					β⁺β⁺ (rare)	²⁴²Pu
²⁴³Cm	96	147	243.0613891(22)	29.1(1) y	α (99.71%)	²³⁹Pu	5/2+
					EC (.29%)	²⁴³Am
					SF (5.3×10⁻⁹%)	(various)
^243mCm	87.4(1) keV			1.08(3) µs			1/2+
²⁴⁴Cm^{[n 3]}	96	148	244.0627526(20)	18.10(2) y	α	²⁴⁰Pu	0+
²⁴⁴Cm^{[n 3]}	96	148	244.0627526(20)	18.10(2) y	SF (1.34×10⁻⁴%)	(various)	0+
^244mCm	1040.188(12) keV			34(2) ms	IT	²⁴⁴Cm	6+
²⁴⁵Cm	96	149	245.0654912(22)	8.5(1)×10³ y	α	²⁴¹Pu	7/2+
²⁴⁵Cm	96	149	245.0654912(22)	8.5(1)×10³ y	SF (6.1×10⁻⁷%)	(various)	7/2+
^245mCm	355.90(10) keV			290(20) ns			1/2+
²⁴⁶Cm	96	150	246.0672237(22)	4.76(4)×10³ y	α (99.97%)	²⁴²Pu	0+
²⁴⁶Cm	96	150	246.0672237(22)	4.76(4)×10³ y	SF (.0261%)	(various)	0+
²⁴⁷Cm	96	151	247.070354(5)	1.56(5)×10⁷ y	α	²⁴³Pu	9/2−
²⁴⁸Cm	96	152	248.072349(5)	3.48(6)×10⁵ y	α (91.74%)	²⁴⁴Pu	0+
					SF (8.26%)	(various)
					β⁻β⁻ (rare)	²⁴⁸Cf
²⁴⁹Cm	96	153	249.075953(5)	64.15(3) min	β⁻	²⁴⁹Bk	1/2(+)
^249mCm	48.758(17) keV			23 µs			(7/2+)
²⁵⁰Cm	96	154	250.078357(12)	8,300# y	SF (80%)^{[n 5]}	(various)	0+
					α (11%)	²⁴⁶Pu
					β⁻ (9%)	²⁵⁰Bk
²⁵¹Cm	96	155	251.082285(24)	16.8(2) min	β⁻	²⁵¹Bk	(1/2+)
²⁵²Cm	96	156	252.08487(32)#	<1 d	β⁻	²⁵²Bk	0+

↑ Abbreviations:
CD: Cluster decay
EC: Electron capture
IT: Isomeric transition
SF: Spontaneous fission
↑ Bold for stable isotopes
1 2 Most common isotopes
↑ Heaviest known nuclide to undergo cluster decay
↑ Lightest nuclide to undergo spontaneous fission as the main decay mode

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.

References

↑ 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.
↑ Specifically from thermal neutron fission of U-235, e.g. in a typical nuclear reactor.
↑ 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."
↑ This is the heaviest isotope with a half-life of at least four years before the "Sea of Instability".
↑ 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.
↑ "Universal Nuclide Chart". nucleonica. (registration required (help)).

Isotope masses from:
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
Isotopic compositions and standard atomic masses from:
- J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005.
- N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.

Isotopes of americium	Isotopes of curium	Isotopes of berkelium
Table of nuclides

Isotopes of the chemical elements
1 H																	2 He
3 Li	4 Be											5 B	6 C	7 N	8 O	9 F	10 Ne
11 Na	12 Mg											13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
19 K	20 Ca	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
37 Rb	38 Sr	39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
55 Cs	56 Ba		72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
87 Fr	88 Ra		104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Uut	114 Fl	115 Uup	116 Lv	117 Uus	118 Uuo

		57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu
		89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr
Table of nuclides Categories: Isotopes Tables of nuclides Metastable isotopes Isotopes by element

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