An intensely radioactive metallic element found (combined) in minute quantities in pitchblende, and various other uranium minerals. Symbol,
Ra; atomic weight, 226.4. Radium was discovered by
M. and
Mme. Curie, of Paris, who in 1902 separated compounds of it by a tedious process from pitchblende. Its compounds color flames carmine and give a characteristic spectrum. It is divalent, resembling barium chemically. The main isotope of radium found in pitchblende, radium-226, has a half-life of 1620 years, decaying first by alpha emission to
radon.
(Chem.) See: radon