Periodic Table of the Elements Rubidium
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rubidium (symbol Rb) Silver-white metallic element of the alkali metals (group I of the periodic table). It ignites spontaneously in air and can be liquid at room temperature. It was discovered in 1861 by the German chemist Robert Bunsen and the German physicist Gustav Kirchhoff. The element has few commercial uses; small amounts are used in photoelectric cells, vacuum-tube filaments, and batteries. It chemically resembles sodium but is more reactive. Properties: at. no.37; r.a.m. 85.4678; r.d. 1.53; m.p. 38.89°C (102°F); b.p. 688°C (1270°F); most common isotope Rb85 (72.15%).