Definitions for radiumˈreɪ di əm

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Princeton's WordNet

  1. radium, Ra, atomic number 88(noun)

    an intensely radioactive metallic element that occurs in minute amounts in uranium ores


  1. Radium(n.)

    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. Radium preparations are remarkable for maintaining themselves at a higher temperature than their surroundings, and for their radiations, which are of three kinds: alpha rays, beta rays, and gamma rays (see these terms). The beta and gamma rays seen in radium preparations are in fact due to disintegration of decay products of radium rather than the radium itself. By reason of these rays they ionize gases, affect photographic plates, cause sores on the skin, and produce many other striking effects. Their degree of activity depends on the proportion of radium present, but not on its state of chemical combination or on external conditions. The radioactivity of radium is therefore an atomic property, and is due to an inherent instability of the atomic nucleus which causes its decay in a process whose rate is first order. The disintegration of the radium nucleus is only the first in a series of nuclear disintegrations leading to production of a series of elements and isotopes. The chain has at least seven stages; the successive main products have been studied and are radon, a gaseous radioactive element belonging chemically to the inert noble gas series (originally called radium emanation or exradio, radium A, radium B, radium C, etc. The successive products are unstable isotopes of several different elements, each with an atomic weight a little lower than its predecessor. Lead is the stable end product. At the same time, the light gas helium is formed, being generated when the expelled alpha particles (positively charged helium nuclei) acquire electrons. Radium, in turn, is formed in the pitchblende ore by a slow disintegration of uranium. Natural radium and also an isotope (radium-228, also called mesothorium I) formed by the decay of thorium, were at one time used to make a luminous paint for watch dials, until the danger of the radioactivity became fully appreciated, and use of such material in watches was discontinued. See also mesothorium.

  2. Origin: [NL., fr. L. radius ray.]


  1. radium(Noun)

    a radioactive metallic chemical element (symbol Ra) with an atomic number of 88.

  2. Origin: radio- (from radioactive) + -ium


  1. Radium

    Radium is a chemical element with symbol Ra and atomic number 88. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, which has a half-life of 1601 years and decays into radon gas. Because of such instability, radium is luminescent, glowing a faint blue. Radium, in the form of radium chloride, was discovered by Marie Skłodowska-Curie and Pierre Curie in 1898. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1910. Since its discovery, it has given names like radium A and radium C2 to several isotopes of other elements that are decay products of radium-226. In nature, radium is found in uranium ores in trace amounts as small as a seventh of a gram per ton of uraninite. Radium is not necessary for living organisms, and adverse health effects are likely when it is incorporated into biochemical processes because of its radioactivity and chemical reactivity.

U.S. National Library of Medicine

  1. Radium

    Radium. A radioactive element of the alkaline earth series of metals. It has the atomic symbol Ra, atomic number 88, and atomic weight 226. Radium is the product of the disintegration of uranium and is present in pitchblende and all ores containing uranium. It is used clinically as a source of beta and gamma-rays in radiotherapy, particularly BRACHYTHERAPY.

The Foolish Dictionary, by Gideon Wurdz


    A radiant radiator, redolent of ranging radial rays of radio-activity, raised to radical rates and regarded as a ruthless rake-off in the reign of riches within the arrayed radius of a raging, raving and raided race.

Editors Contribution

  1. radium

    Is a chemical element.

    In nature, radium is found in uranium and thorium ores in trace amounts as small as a seventh of a gram per ton of uraninite.

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