rubidium

A soft silvery-white metallic element of the alkali group that ignites spontaneously in air and reacts violently with water, used in photocells and as a getter in the manufacture of vacuum tubes. Atomic number 37; atomic weight 85.47; melting point 39.30°C; boiling point 688°C; specific gravity (solid) 1.532; valence 1, 2, 3, 4. cross-reference: Periodic Table.

Chemical symbol, Rb; atomic weight, 85.25. A metal belonging to the group of elements which includes lithium, sodium, potassium, and cæsium: so named from the reddish tint of its salts.

A rare metallic element of the alkali metal series, atomic number 37. 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, 85.48.

A metallic chemical element (symbol Rb) with an atomic number of 37.

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