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A silvery-white, very reactive, metallic element. Rubidium occurs in concentrations of about 34 ppm in the earth's crust. It is found throughout the world in alkali metal minerals such as rhodizite, lepidolite, and carnallite. It is also present in sea water and mineral springs. Rubidium was discovered by Robert Bunsen and Gustav Kirchhoff in 1861. It is a soft metal with a silvery white color that tarnishes quickly. Rubidium is used in photoelectric cells and as a catalyst.

Synonyms and Related Terms

Rb; rubidio (It., Port., Esp.)

Other Properties

Flame color is dark red to violet. Soluble in acids and ethanol. Decomposes in water.

Composition Rb (atomic no. 37)
CAS 7740-17-7
Melting Point 39
Density 1.532
Molecular Weight atomic wt = 84.4678
Boiling Point 688

Hazards and Safety

Ignites spontaneously in air. Reacts vigorously with halogens and mercury. Metal can burn skin on contact.

Additional Information

Web Elements: Website

Sources Checked for Data in Record

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 682
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976 Comment: discovered 1860
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 8439: discovered 1861