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| Atomic symbol: Cm |
| Atomic number: 96 |
| Atomic weight: (247) |
| Atomic volume: 18.28 cm3/mol |
| Density: 13.5 g/cm3 |
| Period Number: 7 |
| Group number: none |
| Group name: Rare Earth, Actinides |
| Element classification: Metal |
| Phase at room temperature: Solid |
| Melting Point: 1613.2 K |
| Boiling point: K |
| Heat of fusion: 15.0 kJ/mol |
| Heat of vaporization: ? |
| Ionization Energy: 6.02 eV |
| 1st ionization energy: 581 kJ/mole |
| 2nd ionization energy: kJ/mole |
| 3rd ionization energy: kJ/mole |
| Electronegativity: 1.3 |
| Electron affinity: kJ/mole |
| Specific heat: ? |
| Heat atomization: kJ/mole atoms |
| Shells: 2,8,18,32,25,9,2 |
| Electron Shell Configuration: [Rn] 5f7 6d1 7s2 |
| Minimum oxidation number: 0 |
| Maximum oxidation number: 4 |
| Minimum common oxidation number: 0 |
| Maximum common oxidation no: 4 |
Appearance & Characteristics |
| Structure:: fcc: face-centered cubic |
| Color: silvery-white |
| Hardness: mohs |
| Toxicity: ? |
| Characteristics: Radioactive |
| Uses: thermoelec. pwr, n source |
| Reaction with air: ? |
| Reaction with 6M HCl: ? |
| Reaction with 15M HNO3: ? |
| Reaction with 6M NaOH: ? |
| Number of isotopes: 0 |
| Oxide(s): CmO Cm2O3 CmO2 |
| Hydride(s): CmH2 |
| Chloride(s): CmCl3 |
| Atomic Radius: 174 pm |
| Ionic radius (1- ion): pm |
| Ionic radius (1+ ion): pm |
| Ionic radius (2- ion): pm |
| Ionic radius (2+ ion): pm |
| Ionic radius (3+ ion): 111 pm |
| Thermal conductivity: J/m-sec-deg |
| Electrical conductivity: 1/mohm-cm |
| Polarizability: 23 A^3 |
| Source: Synthetic |
| Relative abundance solar system: log |
| Abundance earth's crust: log |
| Estimated crustal abundance: Not Applicable |
| Estimated oceanic abundance: Not Applicable |
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| (Pierre and Marie Curie) Although curium follows americium in the periodic system, it was actually the third transuranium element to be discovered. It was identified by Seaborg, James, and Ghiorso in 1944 at the wartime metallurgical laboratory at the University of 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. Fourteen 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 have disappeared long ago from the natural scene. |
| Minute 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. 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. 242Cm generates about three watts of thermal energy per gram. This compares to one-half watt per gram of 238Pu, suggesting that curium can be used for as a power source. 244Cm 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 microcurie. |
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