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rubidium

rubidium definition

ru·bid·ium (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

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

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