Thorium is a chemical element with symbol Th and atomic number 90. A reactive actinide metal, its chemistry is dominated by the +4 oxidation state; it is silvery and tarnishes black in air, forming the dioxide. It is malleable and moderately hard, with a high melting point. Its most stable isotope, 232Th, is weakly radioactive with a half-life of 14.05 billion years, roughly the age of the universe: it decays very slowly to stable lead. Thorium and uranium are the only two significantly radioactive primordial elements. Thorium is chiefly refined from monazite sands as a byproduct of extracting rare earth metals. It was discovered in 1829 by the Norwegian mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jacob Berzelius, who named it after Thor, the Norse god of thunder. Applications were found for the element in the 19th century, but after its radioactivity was discovered in the early 20th century, its use significantly declined. Thorium has been suggested as a replacement for uranium in nuclear reactors.
Read more: <https://en.wikipedia.org/wiki/Thorium> _______________________________ Today's selected anniversaries: 363: Roman emperor Julian and his army set out from Antioch to attack the Sassanian Empire. <https://en.wikipedia.org/wiki/Julian%27s_Persian_War> 1824: The First Anglo-Burmese War, the longest and most expensive war in British Indian history, began. <https://en.wikipedia.org/wiki/First_Anglo-Burmese_War> 1943: The Gloster Meteor, the first operational jet fighter for the Allied Powers, made its maiden flight. <https://en.wikipedia.org/wiki/Gloster_Meteor> 1963: Country music stars Patsy Cline, Cowboy Copas, and Hawkshaw Hawkins were killed when their Piper PA-24 Comanche crashed shortly after takeoff in Camden, Tennessee, U.S. <https://en.wikipedia.org/wiki/1963_Camden_PA-24_crash> 1981: The ZX81, a pioneering British home computer, was launched by Sinclair Research and went on to sell over 1.5 million units around the world. <https://en.wikipedia.org/wiki/ZX81> _____________________________ Wiktionary's word of the day: lorn: 1. (obsolete) Doomed; lost. 2. (archaic) Abandoned, forlorn, lonely. <https://en.wiktionary.org/wiki/lorn> ___________________________ Wikiquote quote of the day: War unleashes — at the same time as the reactionary forces of the capitalist world — the generating forces of social revolution which ferment in its depths. --Rosa Luxemburg <https://en.wikiquote.org/wiki/Rosa_Luxemburg> _______________________________________________ Wikipedia Daily Article mailing list. To unsubscribe, visit: https://lists.wikimedia.org/mailman/listinfo/daily-article-l Questions or comments? Contact [email protected]
