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| Atomic Number: | 96 | Atomic Symbol: | Cm | | Atomic Weight: | 247 | Electron Configuration: | 2-8-18-32-25-9-2 | | Shells: | 2,8,18,32,25,9,2 | Filling Orbital: | 5f7 | | Melting Point: | 1340oC | Boiling Point: | oC | | Description: | Man made radioactive metal. |
History(Pierre and Marie Curie)
- Although curium follows americium in the periodic system, it was actually
known before americium and was the third transuranium element to be discovered.
- It was identified by Seaborg, James, and Ghiorso in 1944 at the wartime
Metallurgical Laboratory in Chicago as a result of helium-ion bombardment of
239Pu in the Berkeley, California, 60-inch cyclotron.
- Visible amounts (30Mg) of 242Cm, in the form of the hydroxide, were first
isolated by Werner and Perlman of the University of California in 1947.
- In 1950, Crane, Wallmann, and Cunningham found that the magnetic
susceptibility of microgram samples of CmF3 was of the same magnitude as that of
GdF3.
- This provided direct experimental evidence for assigning an electronic
configuration to Cm^+3.
- In 1951, the same workers prepared curium in its elemental form for the
first time.
IsotopesFourteen isotopes of curium are now known. The most stable,
247Cm, with a half-life of 16 million years, is so short compared to the earth's
age that any primordial curium must ahve disappeared long ago from the natural
scene.
OccurenceMinute amounts of curium probably exist in natural deposits of
uranium, as a result of a sequence of neutron captures and beta decays sustained
by the very low flux of neutrons naturally present in uranium ores. The presence
of natural curium, however, has never been detected. 242Cm and 244Cm are
available in multigram quantities. 248Cm has been produced only in milligram
amounts.
Properties- Curium is similar in some regards to gadolinium, its rare earth homolog, but
it has a more complex crystal structure.
- Curium is silver in color, is chemically reactive, and is more
electropositive than aluminum.
- Most compounds of trivalent curium are faintly yellow in color.
- 242 Cm generates about three watts of thermal energy per gram.
- This compares to one-half watt per gram of 238Pu.
- This suggests use for curium as a power source.
Costs & Handling244Cm is now offered for sale at $100/mg. Curium
absorbed into the body accumulates in the bones, and is therefore very toxic as
its radiation destroys the red-cell forming mechanism. The maximum permissible
total body burden of 244Cm (soluble) in a human being is 0.3 microcure
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