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radium definition

ra·dium (rā′dē əm)

noun

a radioactive, metallic chemical element, one of the alkaline-earth metals, found in very small amounts in pitchblende and other minerals containing uranium: it undergoes spontaneous atomic disintegration through several stages, emitting alpha, beta, and gamma rays and finally forming an isotope of lead: radium is used in neutron sources and in the treatment of cancer and other diseases: symbol, Ra; at. no., 88

Etymology: ModL < L radius, ray (see radius) + -ium: so named (1898) by P. & M. Curie & G. Bémont, because it emits rays

Webster's New World College Dictionary Copyright © 2009 by Wiley Publishing, Inc., Cleveland, Ohio.
Used by arrangement with John Wiley & Sons, Inc.

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