Isotopes of curium

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Actinides Half-life Fission products
244Cm 241Puƒ 250Cf 227Ac№ 10–22 y medium m is
meta		 85Kr 113mCd₡
232Uƒ 238Pu 243Cmƒ 29–90 y 137Cs 90Sr 151Sm₡ 121mSn
ƒ for
fissile		 249Cfƒ 242mAmƒ 251Cfƒ[1] 140 y –
1.6 ky

No fission products
have a half-life in the
range of 91 y – 210 ky
241Am 226Ra№[2] 247Bk
240Pu 229Th 246Cm 243Am 5–7 ky
4n 245Cmƒ 250Cm 239Puƒ 8–24 ky
236Npƒ 233Uƒ 230Th№ 231Pa№ 32–160 ky
248Cm 4n+1 234U№ 211–348 ky 99Tc ₡ can capture 126Sn 79Se
236U 237Np 242Pu 247Cmƒ 0.37–23 My 135Cs₡ 93Zr 107Pd 129I long
244Pu № for
NORM		 4n+2 4n+3 80 My 6-7% 4-5% 1.25% 0.1-1% <0.05%
232Th№ 238U№ 235Uƒ№ 0.7–14 Gy fission product yield[3]

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.

Trace quantities are found in nature from neutron capture by uranium atoms.[4]

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 [edit]

nuclide
symbol		 Z
(p)		 N
(n)		 isotopic mass
(u)		 half-life decay
mode(s)[5][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 [edit]

  • 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 [edit]

  1. ^ Note: This is the heaviest isotope with a half-life of at least ten years before the "Sea of Instability".
  2. ^ Note: Radium (element 88) is actually a sub-actinide, but 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 ten 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 1600 years, thus merits inclusion here.
  3. ^ Note: specifically from thermal neutron fission of U-235, e.g. in a typical nuclear reactor.
  4. ^ Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements (New ed.). New York, NY: Oxford University Press. ISBN 978-0-19-960563-7. 
  5. ^ http://www.nucleonica.net/unc.aspx


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
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