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| Thorium (Th) a radioactive metal Properties atomic number 90 melting point 1750.0°C (3182.0°F) Pure thorium is a silvery white metal. When contaminated with the oxide, however, it tarnishes in air, becoming gray and, eventually, black. When heated in air, thorium metal ignites and burns with a white light. There are nine isotopes, but the only one found in abundance is thorium-232. Occurence and Sources Thorium is found in small amounts in most rocks and soils, where it is about three times more abundant than uranium, but the only important commercial source of thorium is the rare earth phosphate mineral monazite. The largest deposits of monazite are found in India, with Brazil, Australia, and the United States also having significant deposits. Low demand makes working mines for extraction of thorium alone not profitable, and it is almost always extracted with the rare earths, which themselves may be by-products of production of other minerals. monazite Uses A magnesium-thorium alloy containing about 3 percent thorium is used in the skins of missiles and supersonic aircraft because of the alloy's strength at high temperatures and its lightness. Other magnesium-thorium alloys are used in other high temperature applications. Thorium oxide was once commonly used as the light source in mantles for gas lanterns, but that use has greatly declined in favor of other materials. Thorium-232 has been suggested as a replacement for uranium as fuel in nuclear reactors, and several thorium reactors have been built. History Thorium was identified as an element in 1828 by Jöns Jacob Berzelius, who named it after Thor, the Norse god of thunder. See Also |
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>> Chemical Elements This page was last updated on 08/17/2018. |