Lanthanum

[lænθәnәm]

Definition

(noun.) a white soft metallic element that tarnishes readily; occurs in rare earth minerals and is usually classified as a rare earth.

Checked by Desmond--From WordNet

Definition

(n.) A rare element of the group of the earth metals, allied to aluminium. It occurs in certain rare minerals, as cerite, gadolinite, orthite, etc., and was so named from the difficulty of separating it from cerium, didymium, and other rare elements with which it is usually associated. Atomic weight 138.5. Symbol La.

Edited by Barton

Definition

n. a metal discovered in 1839 in cerite a hydrated silicate of cerium.—Also Lan′thānium.

Checked by Aurora