thorium

American  

[thawr-ee-uhm, thohr-] / ˈθɔr i əm, ˈθoʊr- /

noun

Chemistry.

1. 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. Th; 232.038; 90; 11.7.

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thorium British  

/ ˈθɔːrɪəm /

noun

1. 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

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thorium Scientific  

/ thôr′ē-əm /

1. 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.

2. See Periodic Table

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Other Word Forms

• thoric adjective

Etymology

Origin of thorium

< New Latin (1829); Thor, -ium

Example Sentences

These intense conditions allowed radioactive elements such as uranium and thorium to move upward.

From Science Daily

Unlike uranium, thorium doesn't dissolve well in water, so it precipitates out on particles in the water column.

From Science Daily

Weathering may have ultimately concentrated heat-producing elements like uranium, thorium and potassium in the shallow crust, allowing the deeper crust to cool and harden.

From Science Daily

Heavy elements may result from this "nucleosynthesis"; in fact, half of the heavy isotopes up to bismuth and all of thorium and uranium in the universe may have been created by the r process.

From Science Daily

It forms through the radioactive decay of uranium and thorium deep in the crust and eventually seeps out and escapes into space.

From Science Magazine