Dictionary
lan•tha•num
Pronunciation: (lan'thu-num), [key]—
n. Chem.
a rare-earth, trivalent, metallic element, allied to aluminum, found in certain minerals, as monazite.
Symbol: La;
at. wt.: 138.91;
at. no.: 57;
sp. gr.: 6.15 at 20°C.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.