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thorium

[thawr-ee-uhm, thohr-]

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.



thorium

/ 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

“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

thorium

  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
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Word History and Origins

Origin of thorium1

< New Latin (1829); Thor, -ium
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Word History and Origins

Origin of thorium1

C19: New Latin, from Thor + -ium
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Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

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

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

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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.

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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.

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

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thoritethorium dioxide