- a grayish-white, lustrous, somewhat ductile and malleable, radioactive metallic element present in monazite: used as a source of nuclear energy, as a coating on sun-lamp and vacuum-tube filament coatings, and in alloys. Symbol: Th; atomic weight: 232.038; atomic number: 90; specific gravity: 11.7.
Origin of thorium
Examples from the Web for thorium
He was also the person who first identified silicon, selenium, thorium, and serium.After Dominick
J. J. Berzelius
November 7, 2008
A million bucks of thorium with a hundred years of life in it—have a heart, mister!The Syndic
The substance ranking next in radio-activity to radium is thorium.Inventors at Work
Similar phenomena were observed when radium was substituted for thorium.A Brief Account of Radio-activity
Francis Preston Venable
Thorium and uranium, proportionality of, in older rocks, 26.The Birth-Time of the World and Other Scientific Essays
J. (John) Joly
Emperor of all the metal molecules and king of the thorium spurs.Rip Foster in Ride the Gray Planet
Harold Leland Goodwin
- a soft ductile silvery-white metallic element. It is radioactive and occurs in thorite and monazite: used in gas mantles, magnesium alloys, electronic equipment, and as a nuclear power source. Symbol: Th; atomic no: 90; atomic wt: 232.0381; half-life of most stable isotope, 232 Th: 1.41 × 10 10 years; valency: 4; relative density: 11.72; melting pt: 1755°C; boiling pt: 4788°C
Word Origin and History for thorium
rare metallic element, 1832, Modern Latin, named 1828-9 by its discoverer, Swedish chemist Jöns Jakob Berzelius (1779-1848) in honor of the Scandinavian god Thor.
- A radioactive metallic element that is used in magnesium alloys; its longest-lived isotope, Th 232, has a half-life of 1.41 X 1010 years. Atomic number 90.
- A silvery-white, radioactive metallic element of the actinide series. It is used for fuel in some nuclear reactors and for improving the high-temperature strength of magnesium alloys. The only naturally occurring isotope of thorium, Th 232, is also its most stable, having a half-life of 14.1 billion years. Atomic number 90; atomic weight 232.038; approximate melting point 1,750°C; approximate boiling point 4,500°C; approximate specific gravity 11.7; valence 4. See Periodic Table.