a rare, grayish, radioactive, metallic chemical element, one of the actinides, found in monazite and thorite: it is used in magnesium alloys, the making of gas mantles, electronic equipment, etc., and as a nuclear fuel: symbol, Th; at. no., 90
Origin of thoriumModL: so named (1829) by Baron Jöns Jakob Berzelius, its discoverer ; from Old Norse Thorr (see Thor) + -ium
A radioactive silvery-white metallic element that is recovered commercially from monazite. Its longest-lived isotope, the only one that occurs naturally, is Th-232 with a half-life of 14.1 billion years and is used as a nuclear fuel. Thorium is used in magnesium alloys, and its oxide is widely used in gas mantles of Welsbach burners. Atomic number 90; atomic weight 232.038; melting point 1,750°C; boiling point 4,788°C; specific gravity 11.72; valence 4. See Periodic Table.
Origin of thoriumAfter Thor.
- A chemical element (symbol Th) with atomic number 90.