Difference between revisions of "Curium" - New World Encyclopedia
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'''Curium''' (chemical symbol '''Cm''', [[atomic number]] 96) is a [[Radioactive decay|radioactive]], [[metal]]lic, [[transuranic element]]<ref>"Transuranic elements" are the [[chemical element]]s with [[atomic number]]s greater than that of [[uranium]] (atomic number 92).</ref> of the [[actinide]] series. It is produced synthetically by bombarding [[plutonium]] with [[alpha particle]]s ([[helium]] [[ion]]s). It was named after [[Marie Curie]] and her husband [[Pierre Curie|Pierre]]. | '''Curium''' (chemical symbol '''Cm''', [[atomic number]] 96) is a [[Radioactive decay|radioactive]], [[metal]]lic, [[transuranic element]]<ref>"Transuranic elements" are the [[chemical element]]s with [[atomic number]]s greater than that of [[uranium]] (atomic number 92).</ref> of the [[actinide]] series. It is produced synthetically by bombarding [[plutonium]] with [[alpha particle]]s ([[helium]] [[ion]]s). It was named after [[Marie Curie]] and her husband [[Pierre Curie|Pierre]]. | ||
+ | |||
+ | Two [[isotope]]s of curium (curium-242 and curium-244) can be produced in multigram amounts, making it feasible to study the element's chemical properties. The isotope curium-242 is the precursor to [[plutonium]]-238, which is the most common fuel for [[radioisotope thermoelectric generator]]s (RTGs). Other curium isotopes (Cu-243, Cu-244) are also being investigated for their potential as fuels for RTGs. | ||
== History == | == History == | ||
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== Notable characteristics == | == Notable characteristics == | ||
− | Curium is an [[inner transition metal]] (or actinide) that lies in period 7 of the [[periodic table]], between [[americium]] and [[berkelium]]. | + | Curium is an [[inner transition metal]] (or actinide) that lies in period 7 of the [[periodic table]], between [[americium]] and [[berkelium]]. It does not occur in nature. |
− | The [[isotope]] curium-248 has been synthesized only in milligram quantities, but curium-242 and curium-244 are made in multigram amounts, which allows for the determination of some of the element's properties. Curium-244 can be made in quantity by subjecting [[plutonium]] to [[neutron]] bombardment | + | The [[isotope]] curium-248 has been synthesized only in milligram quantities, but curium-242 and curium-244 are made in multigram amounts, which allows for the determination of some of the element's properties. Curium-244 can be made in quantity by subjecting [[plutonium]] to [[neutron]] bombardment. |
− | A [[rare earth]] homolog, curium is somewhat chemically similar to [[gadolinium]] but with a more complex [[crystal structure]]. Chemically reactive, its [[metal]] is silvery-white in color and the element is more [[electropositive]] than [[ | + | A [[rare earth]] homolog, curium is somewhat chemically similar to [[gadolinium]] but with a more complex [[crystal structure]]. Chemically reactive, its [[metal]] is silvery-white in color and the element is more [[electropositive]] than [[aluminum]] (most trivalent curium [[compound (chemistry)|compound]]s are slightly yellow). |
− | |||
− | |||
=== Isotopes === | === Isotopes === | ||
− | Many [[radioisotope]]s of curium have been characterized, with the most stable being Cm-247 with a [[half-life]] of 1.56 × 10<sup>7</sup> [[year]]s | + | Many [[radioisotope]]s of curium have been characterized, with the most stable being Cm-247, with a [[half-life]] of 1.56 × 10<sup>7</sup> [[year]]s; Cm-248, with a half-life of 3.40 × 10<sup>5</sup> years; Cm-250, with a half-life of 9000 years; and Cm-245, with a half-life of 8500 years. All the remaining [[radioactive]] isotopes have half-lives of less than 30 years, and the majority of these have half-lives that are less than 33 days. This element also has 4 [[meta state]]s, with the most stable being Cm-244m (t<sub>½</sub> 34 ms). The isotopes of curium range in [[atomic weight]] from 233.051 [[atomic mass unit|amu]] (Cm-233) to 252.085 amu (Cm-252). |
== Compounds == | == Compounds == | ||
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**curium trioxide (Cm<sub>2</sub>O<sub>3</sub>) | **curium trioxide (Cm<sub>2</sub>O<sub>3</sub>) | ||
* Halides: | * Halides: | ||
+ | **curium tetrafluoride (Cm[[Fluorine|F]]<sub>4</sub>) | ||
+ | **curium chloride (Cm[[chlorine|Cl]]<sub>3</sub>) | ||
**curium bromide (Cm[[bromine|Br]]<sub>3</sub>) | **curium bromide (Cm[[bromine|Br]]<sub>3</sub>) | ||
− | |||
− | |||
**curium iodide (Cm[[iodine|I]]<sub>3</sub>) | **curium iodide (Cm[[iodine|I]]<sub>3</sub>) | ||
+ | |||
+ | == Applications == | ||
+ | |||
+ | Curium has been studied extensively as a potential fuel for [[RTG|Radioisotope thermoelectric generators]]. Curium-242 can generate up to 120 [[watt]]s of thermal [[energy]] per gram (W/g). Its very short half-life, however, makes it unsuitable as a power source for long-term use. Curium-242 is the precursor to [[plutonium]]-238, which is the most common fuel for RTGs. Curium-244 has also been studied as an energy source for RTGs having a maximum energy density ~3 W/g, but produces a large amount of neutron radiation from [[Spontaneous_fission|spontaneous fission]]. Curium-243, with a roughly 30-year half-life and good energy density (about 1.6 W/g), would seem to make an ideal fuel, but it produces significant amounts of [[Gamma_ray|gamma]] and [[Beta_ray|beta]] radiation from radioactive decay products. | ||
== Nuclear fuel cycle == | == Nuclear fuel cycle == | ||
The [[MOX]] which is to be used in power reactors should contain little or no curium as the neutron activation of this element will create [[californium]] which is a strong [[neutron]] emitter. The californium would [[pollute]] the back end of the fuel cycle and increase the dose to workers. Hence if the [[Minor actinides]] are to be used as fuel in a thermal neutron reactor the curium should be excluded from the fuel or placed in special fuel rods where it is the only actinide present. | The [[MOX]] which is to be used in power reactors should contain little or no curium as the neutron activation of this element will create [[californium]] which is a strong [[neutron]] emitter. The californium would [[pollute]] the back end of the fuel cycle and increase the dose to workers. Hence if the [[Minor actinides]] are to be used as fuel in a thermal neutron reactor the curium should be excluded from the fuel or placed in special fuel rods where it is the only actinide present. | ||
+ | |||
+ | == Biological effects == | ||
+ | |||
+ | Curium [[bio-accumulate]]s in [[bone]] tissue where its radiation destroys [[bone marrow]] and thus stops the production of [[red blood cell]]s. | ||
== See also == | == See also == |
Revision as of 17:20, 21 March 2007
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General | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Name, Symbol, Number | curium, Cm, 96 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Chemical series | actinides | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Group, Period, Block | n/a, 7, f | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Appearance | silvery | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Atomic mass | (247) g/mol | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Electron configuration | [Rn] 5f7 6d1 7s2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Electrons per shell | 2, 8, 18, 32, 25, 9, 2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Physical properties | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Phase | solid | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Density (near r.t.) | 13.51 g/cm³ | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Melting point | 1613 K (1340 °C, 2444 °F) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Boiling point | 3383 K (3110 °C, 5630 °F) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Heat of fusion | ? 15 kJ/mol | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Atomic properties | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Crystal structure | hexagonal close-packed | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Oxidation states | 3 (amphoteric oxide) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Electronegativity | 1.3 (Pauling scale) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Ionization energies | 1st: 581 kJ/mol | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Miscellaneous | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Magnetic ordering | no data | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
CAS registry number | 7440-51-9 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Notable isotopes | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Curium (chemical symbol Cm, atomic number 96) is a radioactive, metallic, transuranic element[1] of the actinide series. It is produced synthetically by bombarding plutonium with alpha particles (helium ions). It was named after Marie Curie and her husband Pierre.
Two isotopes of curium (curium-242 and curium-244) can be produced in multigram amounts, making it feasible to study the element's chemical properties. The isotope curium-242 is the precursor to plutonium-238, which is the most common fuel for radioisotope thermoelectric generators (RTGs). Other curium isotopes (Cu-243, Cu-244) are also being investigated for their potential as fuels for RTGs.
History
Curium was first synthesized at the University of California, Berkeley by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944. The team named the new element after Marie Curie and her husband Pierre, who are famous for their work on radioactivity and the discovery of radium and polonium.
Curium was the third transuranic element to be discovered. The isotope curium-242 (half-life 163 days) was made by bombarding a plutonium-239 target with alpha particles in the 60-inch cyclotron at Berkeley. The element was chemically identified at the Metallurgical Laboratory (now Argonne National Laboratory) at the University of Chicago.
Louis Werner and Isadore Perlman created a visible sample of curium-242 hydroxide at the University of California in 1947 by bombarding americium-241 with neutrons. The elemental form of curium was prepared for the first time in 1951.
Notable characteristics
Curium is an inner transition metal (or actinide) that lies in period 7 of the periodic table, between americium and berkelium. It does not occur in nature.
The isotope curium-248 has been synthesized only in milligram quantities, but curium-242 and curium-244 are made in multigram amounts, which allows for the determination of some of the element's properties. Curium-244 can be made in quantity by subjecting plutonium to neutron bombardment.
A rare earth homolog, curium is somewhat chemically similar to gadolinium but with a more complex crystal structure. Chemically reactive, its metal is silvery-white in color and the element is more electropositive than aluminum (most trivalent curium compounds are slightly yellow).
Isotopes
Many radioisotopes of curium have been characterized, with the most stable being Cm-247, with a half-life of 1.56 × 107 years; Cm-248, with a half-life of 3.40 × 105 years; Cm-250, with a half-life of 9000 years; and Cm-245, with a half-life of 8500 years. All the remaining radioactive isotopes have half-lives of less than 30 years, and the majority of these have half-lives that are less than 33 days. This element also has 4 meta states, with the most stable being Cm-244m (t½ 34 ms). The isotopes of curium range in atomic weight from 233.051 amu (Cm-233) to 252.085 amu (Cm-252).
Compounds
Known compounds of curium include the following:
- Oxides:
- curium dioxide (CmO2)
- curium trioxide (Cm2O3)
- Halides:
Applications
Curium has been studied extensively as a potential fuel for Radioisotope thermoelectric generators. Curium-242 can generate up to 120 watts of thermal energy per gram (W/g). Its very short half-life, however, makes it unsuitable as a power source for long-term use. Curium-242 is the precursor to plutonium-238, which is the most common fuel for RTGs. Curium-244 has also been studied as an energy source for RTGs having a maximum energy density ~3 W/g, but produces a large amount of neutron radiation from spontaneous fission. Curium-243, with a roughly 30-year half-life and good energy density (about 1.6 W/g), would seem to make an ideal fuel, but it produces significant amounts of gamma and beta radiation from radioactive decay products.
Nuclear fuel cycle
The MOX which is to be used in power reactors should contain little or no curium as the neutron activation of this element will create californium which is a strong neutron emitter. The californium would pollute the back end of the fuel cycle and increase the dose to workers. Hence if the Minor actinides are to be used as fuel in a thermal neutron reactor the curium should be excluded from the fuel or placed in special fuel rods where it is the only actinide present.
Biological effects
Curium bio-accumulates in bone tissue where its radiation destroys bone marrow and thus stops the production of red blood cells.
See also
Notes
- ↑ "Transuranic elements" are the chemical elements with atomic numbers greater than that of uranium (atomic number 92).
ReferencesISBN links support NWE through referral fees
- Emsley, John. 2001. Nature's Building Blocks: An A–Z Guide to the Elements. Oxford: Oxford Univ. Press. ISBN 0198503407 and ISBN 978-0198503408.
- Greenwood, N.N., and A. Earnshaw. 1998. Chemistry of the Elements 2nd ed. Oxford, UK; Burlington, MA: Butterworth-Heinemann. ISBN 0750633654. Online version.
- Hampel, Clifford A. 1968. The Encyclopedia of the Chemical Elements. New York: Reinhold Book Corp. ISBN 0442155980 and ISBN 978-0442155988.
- Morss, Lester R., Norman M. Edelstein, and Jean Fuger, eds. 2006. The Chemistry of the Actinide and Transactinide Elements. 3rd ed. 5 vols. Joseph J. Katz, adapter. Dordrecht: Springer. ISBN 1402035551 and ISBN 978-1402035555.
- Stwertka, Albert. 1998. Guide to the Elements. Rev. ed. Oxford: Oxford University Press. ISBN 0-19-508083-1.
- Chemistry Operations. 2003. "Curium" Los Alamos National Laboratory, Chemistry Division. Retrieved March 14, 2007.
External links
- It's Elemental - Curium
- Human Health Fact Sheet on Curium
- WebElements.com - Curium
- NLM Hazardous Substances Databank – Curium, Radioactive
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