Curium (96)

Curium

Curium [KYOOR-ee-um] is a hard, brittle, radioactive silvery metal. It does not occur in nature and must be made in a nuclear reactor by neutron capture reactions from plutonium and americium isotopes. It tarnishes slowly in dry air at room temperature.

Most compounds of Cm(III) are faintly yellow. If curium enters the body it accumulates in the bones, and is therefore very toxic as its radiation destroys the red-cell forming mechanism. Curium is a radioactive rare earth metal. The most stable isotope is ²⁴⁷Cm which has a half-life of 16 million years. Curium is probably present in uranium ores. It has a few specialized uses but only a few of its compounds are known.

Name: Curium Symbol: Cm Atomic number: 96 Atomic weight: [ 247 ] Standard state: solid at 298 K CAS Registry ID: 7440-51-9

Group name: Actinoid Period in periodic table: 7 (actinoid) Block in periodic table: f-block Color: silver Classification: Metallic

Historical information

Curium was discovered by Glenn T. Seaborg, Ralph A. James, Albert Ghiorso at 1944 in USA (Berkley again!). Origin of name comes from the pair Pierre and Marie "Curie" – discoverers of Radium.

Curium was identified by Seaborg and others in 1944 as a result of helium ion bombardment of the plutonium isotope ²³⁹Pu with α-particles.  This was then sent to the Metallurgical Laboratory at the University of Chicago where a tiny sample of curium was eventually separated and identified. However, news of the new element was not disclosed until after the end of World War II. Most unusually, it was first revealed by Seaborg when he appeared as the guest scientist on a radio show for children on 11 November 1945. It was officially announced the following week.Three years later visible amounts of the hydroxide were isolated in visible quantities as the hydroxide, Cm(OH)₃,by Werner and Perlman. In 1951, the same workers prepared curium in its elemental form for the first time.

Physical properties

• Melting point: 1613 [or 1340 °C (2444 °F)] K
• Boiling point: 3383 [or 3110 °C (5630 °F)] K
• Density of solid: 13510 kg m^-3

Orbital properties

• Ground state electron configuration:  [Rn].5f⁷.6d¹.7s²
• Shell structure:  2.8.18.32.25.9.2
• Term symbol:   ⁹D₂
• Pauling electronegativity: 1.3 (Pauling units)
•  First ionisation energy: 581 kJ mol^-1
•  Second ionisation energy: no data kJ mol^-1

Since only milligram amounts of curium have ever been produced, there are currently no commercial applications for it, although it might be used in radioisotope thermoelectric generators in the future. Curium is primarily used for basic scientific research.

Scientists have produced several curium compounds. They include: curium dioxide (CmO₂), curium trioxide (Cm₂O₃), curium bromide (CmBr₃), curium chloride (CmCl₃), curium chloride (CmCl₃), curium tetrafluoride (CmF₄) and curium iodide (CmI₃). As with the element, the compounds currently have no commercial applications and are primarily used for basic scientific research.