Isotopes of curium

Actinides				Half-life	Fission products
244Cm	241Pu f	250Cf	243Cmf	10–30 y	137Cs	90Sr	85Kr
232U  f		238Pu	f is for fissile	69–90 y			151Sm nc➔
4n	249Cf  f	242Amf		141–351	No fission product has half-life 102 to 2×105 years
	241Am		251Cf  f	431–898
240Pu	229Th	246Cm	243Am	5–7 ky
4n	245Cmf	250Cm	239Pu f	8–24 ky
	233U    f	230Th	231Pa	32–160
	4n+1	234U	4n+3	211–290	99Tc		126Sn	79Se
248Cm		242Pu		340–373	Long-lived fission products
	237Np	4n+2		1–2 My	93Zr	135Cs nc➔
236U	4n+1		247Cmf	6–23 My		107Pd	129I
244Pu				80 My	>7%	>5%	>1%	>.1%
232Th		238U	235U    f	0.7–12 Ty	fission product yield

Curium (Cm) 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 synthesized was ²⁴²Cm in 1944.

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. 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)[1][n 1]	daughter isotopes[n 2]	spin
	excitation energy
232Cm	96	136		1? min			0+
233Cm	96	137	233.05077(8)	1# min	β+	233Am	3/2+#
					α	229Pu
234Cm	96	138	234.05016(2)	51(12) s	β+	234Am	0+
					α	230Pu
235Cm	96	139	235.05143(22)#	5# min	β+	235Am	5/2+#
					α	231Pu
236Cm	96	140	236.05141(22)#	10# min	β+	236Am	0+
					α	232Pu
237Cm	96	141	237.05290(22)#	20# min	β+	237Am	5/2+#
					α	233Pu
238Cm	96	142	238.05303(4)	2.4(1) h	EC (90%)	238Am	0+
					α (10%)	234Pu
239Cm	96	143	239.05496(11)#	~2.9 h	β+ (99.9%)	239Am	(7/2-)
					α (.1%)	235Pu
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+
					α (1%)	237Pu
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) a	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) a	α	240Pu	0+
					SF (1.34×10−4%)	(various)
244mCm	1040.188(12) keV			34(2) ms	IT	244Cm	6+
245Cm	96	149	245.0654912(22)	8.5(1)×103 a	α	241Pu	7/2+
					SF (6.1×10−7%)	(various)
245mCm	355.90(10) keV			290(20) ns			1/2+
246Cm	96	150	246.0672237(22)	4.76(4)×103 a	α (99.97%)	242Pu	0+
					SF (.0261%)	(various)
247Cm	96	151	247.070354(5)	1.56(5)×107 a	α	243Pu	9/2-
248Cm	96	152	248.072349(5)	3.48(6)×105 a	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# a	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+

1. ^ Abbreviations:
   CD: Cluster decay
   EC: Electron capture
   IT: Isomeric transition
   SF: Spontaneous fission
2. ^ Bold for stable isotopes
3. ^ ^{a b} Most common isotopes
4. ^ Heaviest known nuclide to undergo cluster decay
5. ^ 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

1. ^ http://www.nucleonica.net/unc.aspx

• Isotope masses from:
  • G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (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. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf. 
• 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 and 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. http://www.iupac.org/publications/pac/75/6/0683/pdf/. 
  • 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. http://iupac.org/publications/pac/78/11/2051/pdf/. 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 and O. Bersillon (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. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf. 
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. http://www.nndc.bnl.gov/nudat2/. 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 978-0849304859. 

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