Dictionary
tho•ri•um
Pronunciation: (thôr'ē-um, thōr'-), [key]—
n. Chem.
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;
at. wt.: 232.038;
at. no.: 90;
sp. gr.: 11.7. Cf.
thoria. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.