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rubidium

(ro̵̅o̅ bid′ē əm)

noun

a soft, silvery-white, metallic chemical element, one of the alkali metals, that ignites spontaneously in air and reacts violently in water: used in photocells and in filaments of vacuum tubes: symbol, Rb; at. no., 37

Origin: ModL: so named (1861) by Robert Wilhelm Bunsen & Gustav Robert Kirchhoff < L rubidus, red < ruber, red (from the red lines in its spectrum) + -ium

See rubidium in American Heritage Dictionary 4

noun Symbol Rb

A soft silvery-white metallic element of the alkali group that ignites spontaneously in air and reacts violently with water, used in photocells and in the manufacture of vacuum tubes. Atomic number 37; atomic weight 85.47; melting point 38.89°C; boiling point 688°C; specific gravity (solid) 1.532; valence 1, 2, 3, 4. See Table at element.

Origin:

Origin: From Latin rūbidus, red; see reudh- in Indo-European roots

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