Radium.

ETYM New Lat., from Latin radius ray.
Rare radioactive metallic element found in pitchblende, etc.
An intensely radioactive metallic element that occurs in minute amounts in uranium ores; SYN. Ra, atomic number 88.
White, radioactive, metallic element, symbol Ra, atomic number 88, atomic weight 226.02. It is one of the alkaline-earth metals, found in nature in pitchblende and other uranium ores. Of the 16 isotopes, the commonest, Ra-226, has a half-life of 1.622 years. The element was discovered and named in 1898 by Pierre and Marie Curie, who were investigating the residues of pitchblende.
Radium decays in successive steps to produce radon (a gas), polonium, and finally a stable isotope of lead. The isotope Ra-223 decays through the uncommon mode of heavy-ion emission, giving off carbon-14 and transmuting directly to lead. Because radium luminesces, it was formerly used in paints that glowed in the dark; when the hazards of radioactivity became known its use was abandoned, but factory and dump sites remain contaminated and many former workers and neighbors contracted fatal cancers. + prikaži više