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A naturally occurring radioactive element. Radium occurs in uranium ores, such as pitchblende, at concentrations of approximately 10-7 ppm. Radium was discovered in 1898 by the Curies. It is a disintegration product of Uranium. Radium is a bright white metal. It undergoes spontaneous disintegration to form Radon gas and alpha rays. Radium was formerly used to make luminous paints used in clock dials, doorknobs, and other glow-in-the-dark items prior to the 1970s.

Synonyms and Related Terms



  • Highly toxic radioactive element.
  • Destroys living tissue.

Physical and Chemical Properties

Soluble in water with the evolution of hydrogen. Radium salts burn with a carmine red flame color. Half life = 1622 years.

Composition Ra (atomic no. 88)
CAS 7440-14-4
Melting Point 700 C
Density 5.0-5.5 g/ml
Molecular Weight atomic wt = 226.026
Boiling Point 1140 C

Resources and Citations

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 649
  • 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
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 8277
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • Edward Reich, Carlton J. Siegler, Consumer Goods: How to Know and Use Them, American Book Company, New York City, 1937