Curium

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Curium (play /ˈkjʊəriəm/ KEWR-ee-əm) is a synthetic chemical element with the symbol Cm and atomic number 96. This radioactive transuranic element of the actinide series was named after Marie Skłodowska-Curie and her husband Pierre Curie. Curium was first intentionally produced and identified in summer 1944 by the group of Glenn T. Seaborg at the University of California, Berkeley. The discovery was kept secret and only released to the public in November 1945. Most curium is produced by bombarding uranium or plutonium with alpha particles (helium ions) in nuclear reactors – one tonne of spent nuclear fuel contains about 20 grams of curium.

Curium is a hard, dense silvery metal with relatively high for actinides melting and boiling points. Whereas it is paramagnetic at ambient conditions, it becomes antiferromagnetic upon cooling, and other magnetic transitions are also observed for many curium compounds. In compounds, curium usually exhibits valence +3 and sometimes +4, and the +3 valence is predominant in solutions. Curium readily oxidizes, and its oxides are a dominant form of this element. It forms strongly fluorescent complexes with various organic compounds, but there is no evidence of its incorporation into bacteria and archaea. When introduced into human body, curium accumulates in the bones, lungs and liver where it promotes cancer.

All known isotopes of curium are highly radioactive and have a small critical mass for a sustained nuclear chain reaction. They predominantly emit alpha particles, and the heat released in this process can potentially produce electricity in radioisotope thermoelectric generators. This application is yet hindered by the scarcity, high cost and radioactivity of curium isotopes. Curium is used in production of heavier actinides and of the 238Pu radionuclide for power sources in artificial pacemakers. It served as the α-source in the alpha particle X-ray spectrometers installed on the Sojourner, Mars, Mars 96, Athena, Spirit and Opportunity rovers in order to analyze the composition and structure of the rocks on the surface of Mars and the Moon. Such spectrometer will also be used by the Philae lander of the Rosetta spacecraft to probe the surface of the 67P/Churyumov-Gerasimenko comet.

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