| 释义 |
WordReference Random House Unabridged Dictionary of American English © 2024tho•ri•um (thôr′ē əm, thōr′-),USA pronunciation n. [Chem.]- Chemistrya 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; at. wt.: 232.038;
at. no.: 90;
sp. gr.: 11.7. Cf. thoria.
- Neo-Latin (1829); see Thor, -ium
Collins Concise English Dictionary © HarperCollins Publishers:: thorium /ˈθɔːrɪəm/ n - 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, 232Th: 1.41 × 1010 years; valency: 4; relative density: 11.72; melting pt: 1755°C; boiling pt: 4788°C
Etymology: 19th Century: New Latin, from Thor + -iumˈthoric adj |