RUBIDIUM

rubidium, Rb, atomic number

(noun) a soft silvery metallic element of the alkali metal group; burns in air and reacts violently in water; occurs in carnallite and lepidolite and pollucite

Source: WordNet® 3.1

Etymology

Noun

rubidium (usually uncountable, plural rubidiums)

The chemical element (symbol Rb) with an atomic number of 37. It is a soft, highly reactive alkali metal.

(countable) A single atom of this element.

Source: Wiktionary

Ru*bid"i*um, n. Etym: [NL., fr. L. rubidus red, fr. rubere to be red. So called from two dark red spectroscopic lines by means of which it was discovered in the lepidolite from Rozena, Moravia. See Rubicund.] (Chem.)

Definition: A rare metallic element. It occurs quite widely, but in small quantities, and always combined. It is isolated as a soft yellowish white metal, analogous to potassium in most of its properties. Symbol Rb. Atomic weight, 85.2.

Source: Webster’s Unabridged Dictionary 1913 Edition