thorium

[ thawr-ee-uh m, thohr- ]

/ ˈθɔr i əm, ˈθoʊr- /

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.

Nearby words

thorez, thorfinn karlsefni, thoria, thorianite, thorite, thorium, thorium dioxide, thorium series, thorn, thorn apple, thorn in one's flesh

Compare thoria.

Origin of thorium

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

Related forms

thor·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

He was also the person who first identified silicon, selenium, thorium, and serium.
After Dominick|J. J. Berzelius|November 7, 2008|DAILY BEAST
But thorium mostly gives off the kind of radiation known as alpha particles.
Rip Foster in Ride the Gray Planet|Harold Leland Goodwin
The manufacturers give away a pound of cerium salts with every purchase of a hundred pounds of thorium salts.
Creative Chemistry|Edwin E. Slosson
Radium and thorium, but not uranium, give rise to radio-active gases which have been called emanations.
Darwin and Modern Science|A.C. Seward and Others

It will be seen that the ray of greatest range is that proceeding from thorium C2, which reaches a distance of 8.6 cms.
The Birth-Time of the World and Other Scientific Essays|J. (John) Joly
They would be compared with a chunk of thorium of the same size.
Rip Foster in Ride the Gray Planet|Harold Leland Goodwin

British Dictionary definitions for thorium

thorium

/ (ˈθɔːrɪəm) /

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 Forms

thoric, 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

Medicine definitions for thorium

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.

Science definitions for thorium

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.