thorium

[thawr-ee-uh m, thohr-]

noun Chemistry.

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.

Compare thoria.

Origin of thorium

< New Latin (1829); see Thor, -ium

Related formsthor·ic

[thawr-ik, thor-] /ˈθɔr ɪk, ˈθɒr-/, adjective

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for thorium

Contemporary Examples of thorium

He was also the person who first identified silicon, selenium, thorium, and serium.
After Dominick
J. J. Berzelius
November 7, 2008

Historical Examples of thorium

A million bucks of thorium with a hundred years of life in it—have a heart, mister!
The Syndic
C.M. Kornbluth
The substance ranking next in radio-activity to radium is thorium.
Inventors at Work
George Iles
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

British Dictionary definitions for thorium

thorium

noun

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

Derived Formsthoric, adjective

Word Origin for thorium

C19: New Latin, from Thor + -ium

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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.

thorium in Medicine

thorium

[thôr′ē-əm]

n. Symbol Th

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.

thorium in Science

thorium

[thôr′ē-əm]

Th

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.