Curium (96Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic weight cannot be given, and it has no stable isotopes. The first isotope synthesized was 242Cm in 1944, which has 146 neutrons.
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There are 19 known radioisotopes ranging from 233Cm to 251Cm. There are also ten known nuclear isomers. The longest-lived isotope is 247Cm, with half-life 15.6 million years – orders of magnitude longer than that of any known isotope beyond curium, and long enough to study as a possible extinct radionuclide that would be produced by the r-process.[2][3] The longest-lived known isomer is 246mCm with a half-life of 1.12 seconds.
List of isotopes
edit
Nuclide [n 1] |
Z | N | Isotopic mass (Da) [n 2][n 3] |
Half-life [n 4] |
Decay mode [n 5] |
Daughter isotope |
Spin and parity [n 6][n 4] | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy[n 4] | |||||||||||||||||||
233Cm | 96 | 137 | 233.05077(8) | 23 13 −6 s |
β (80%) | 233Am | 3/2 # | ||||||||||||
α (20%) | 229Pu | ||||||||||||||||||
234Cm | 96 | 138 | 234.05016(2) | 52(9) s | β (71%) | 234Am | 0 | ||||||||||||
α (27%) | 230Pu | ||||||||||||||||||
SF (2%) | (various) | ||||||||||||||||||
235Cm[4] | 96 | 139 | 235.05143(22)# | 300 250 −100 s |
β (99.0%) | 235Am | (5/2 ) | ||||||||||||
α (1.0%) | 231Pu | ||||||||||||||||||
236Cm | 96 | 140 | 236.05141(22)# | 6.8(8) min | β (82%) | 236Am | 0 | ||||||||||||
α (18%) | 232Pu | ||||||||||||||||||
SF (<0.1%)[5] | (various) | ||||||||||||||||||
237Cm[6][4] | 96 | 141 | 237.05290(22)# | >660 s | β | 237Am | (5/2 ) | ||||||||||||
α (<1%) | 233Pu | ||||||||||||||||||
238Cm[6] | 96 | 142 | 238.05303(4) | 2.2(4) h | EC (~94%) | 238Am | 0 | ||||||||||||
α (~6%) | 234Pu | ||||||||||||||||||
239Cm[1] | 96 | 143 | 239.05496(11)# | 2.5(4) h | β | 239Am | (7/2−) | ||||||||||||
α (6.2x10−3%) | 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 7] | 96 | 146 | 242.0588358(20) | 162.8(2) d | α[n 8] | 238Pu | 0 | ||||||||||||
SF (6.33×10−6%) | (various) | ||||||||||||||||||
CD (10−14%)[n 9] | 208Pb 34Si | ||||||||||||||||||
242mCm | 2800(100) keV | 180(70) ns | |||||||||||||||||
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 | IT | 243Cm | 1/2 | ||||||||||||||
244Cm[n 7] | 96 | 148 | 244.0627526(20) | 18.10(2) y | α | 240Pu | 0 | ||||||||||||
SF (1.34×10−4%) | (various) | ||||||||||||||||||
244m1Cm | 1040.188(12) keV | 34(2) ms | IT | 244Cm | 6 | ||||||||||||||
244m2Cm | 1100(900)# keV | >500 ns | SF | (various) | |||||||||||||||
245Cm | 96 | 149 | 245.0654912(22) | 8.5(1)×103 y | α | 241Pu | 7/2 | ||||||||||||
SF (6.1×10−7%) | (various) | ||||||||||||||||||
245mCm | 355.92(10) keV | 290(20) ns | IT | 245Cm | 1/2 | ||||||||||||||
246Cm | 96 | 150 | 246.0672237(22) | 4.76(4)×103 y | α (99.97%) | 242Pu | 0 | ||||||||||||
SF (.0261%) | (various) | ||||||||||||||||||
246mCm | 1179.66(13) keV | 1.12(0.24) s | IT | 246Cm | 8− | ||||||||||||||
247Cm | 96 | 151 | 247.070354(5) | 1.56(5)×107 y | α | 243Pu | 9/2− | ||||||||||||
247m1Cm | 227.38(19) keV | 26.3(0.3) μs | IT | 247Cm | 5/2 | ||||||||||||||
247m2Cm | 404.90(3) keV | 100.6(0.6) ns | IT | 247Cm | 1/2 | ||||||||||||||
248Cm | 96 | 152 | 248.072349(5) | 3.48(6)×105 y | α (91.74%) | 244Pu | 0 | ||||||||||||
SF (8.26%) | (various) | ||||||||||||||||||
248mCm | 1458.1(1) keV | 146(18) μs | IT | 248Cm | (8−) | ||||||||||||||
249Cm | 96 | 153 | 249.075953(5) | 64.15(3) min | β− | 249Bk | 1/2( ) | ||||||||||||
249mCm | 48.758(17) keV | 23 μs | α | 245Pu | (7/2 ) | ||||||||||||||
250Cm | 96 | 154 | 250.078357(12) | 8300# y | SF (74%)[n 10] | (various) | 0 | ||||||||||||
α (18%) | 246Pu | ||||||||||||||||||
β− (8%) | 250Bk | ||||||||||||||||||
251Cm | 96 | 155 | 251.082285(24) | 16.8(2) min | β− | 251Bk | (1/2 ) | ||||||||||||
This table header & footer: |
- ^ mCm – Excited nuclear isomer.
- ^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- ^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
- ^ a b c # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
- ^
Modes of decay:
CD: Cluster decay EC: Electron capture SF: Spontaneous fission - ^ ( ) spin value – Indicates spin with weak assignment arguments.
- ^ a b Most common isotopes
- ^ Theoretically capable of β β decay to 242Pu[1]
- ^ Heaviest known nuclide to undergo cluster decay
- ^ The nuclide with the lowest atomic number known to undergo spontaneous fission as the main decay mode
Actinides vs fission products
editActinides[7] by decay chain | Half-life range (a) |
Fission products of 235U by yield[8] | ||||||
---|---|---|---|---|---|---|---|---|
4n | 4n 1 | 4n 2 | 4n 3 | 4.5–7% | 0.04–1.25% | <0.001% | ||
228Ra№ | 4–6 a | 155Euþ | ||||||
248Bk[9] | > 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 | |||||
241Amƒ | 251Cfƒ[10] | 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[11] | ||||||
232Th№ | 238U№ | 235Uƒ№ | 0.7–14.1 Ga | |||||
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References
edit- ^ a b c 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.
- ^ Côté, Benoit; Eichler, Marius; Yagüe López, Andrés; Vassh, Nicole; Mumpower, Matthew R.; Világos, Blanka; Soós, Benjámin; Arcones, Almudena; Sprouse, Trevor M.; Surman, Rebecca; Pignatari, Marco; Pető, Mária K.; Wehmeyer, Benjamin; Rauscher, Thomas; Lugaro, Maria (26 February 2021). "129I and 247Cm in meteorites constrain the last astrophysical source of solar r-process elements". Science. 371 (6532): 945–948. arXiv:2006.04833. Bibcode:2021Sci...371..945C. doi:10.1126/science.aba1111. PMID 33632846. S2CID 232050526.
- ^ Davis, A.M.; McKeegan, K.D. (2014). "Short-Lived Radionuclides and Early Solar System Chronology". Treatise on Geochemistry: 383. doi:10.1016/B978-0-08-095975-7.00113-3. ISBN 9780080983004.
- ^ a b Khuyagbaatar, J.; Heßberger, F. P.; Hofmann, S.; Ackermann, D.; Burkhard, H. G.; Heinz, S.; Kindler, B.; Kojouharov, I.; Lommel, B.; Mann, R.; Maurer, J.; Nishio, K. (12 October 2020). "α decay of Fm 243 143 and Fm 245 145 , and of their daughter nuclei". Physical Review C. 102 (4): 044312. doi:10.1103/PhysRevC.102.044312. ISSN 2469-9985. S2CID 241259726. Retrieved 24 June 2023.
- ^ Khuyagbaatar, J.; Heßberger, F. P.; Hofmann, S.; Ackermann, D.; Comas, V. S.; Heinz, S.; Heredia, J. A.; Kindler, B.; Kojouharov, I.; Lommel, B.; Mann, R.; Nishio, K.; Yakushev, A. (1 October 2010). "The new isotope 236Cm and new data on 233Cm and 237, 238, 240Cf" (PDF). The European Physical Journal A. 46 (1): 59–67. Bibcode:2010EPJA...46...59K. doi:10.1140/epja/i2010-11026-9. ISSN 1434-601X. S2CID 122809010. Retrieved 24 June 2023.
- ^ a b Asai, M.; Tsukada, K.; Ichikawa, S.; Sakama, M.; Haba, H.; Nishinaka, I.; Nagame, Y.; Goto, S.; Kojima, Y.; Oura, Y.; Shibata, M. (20 June 2006). "α decay of 238Cm and the new isotope 237Cm". Physical Review C. 73 (6): 067301. doi:10.1103/PhysRevC.73.067301. Retrieved 24 June 2023.
- ^ 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.
- ^ Specifically from thermal neutron fission of uranium-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. 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]." - ^ This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
- ^ 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.