- The celebrated radioactive element discovered by Marie and Pierre Curie in 1898.
* * *A metallic element, atomic no. 88, extracted in very minute quantities from pitchblende; 226Ra, its longest-lived isotope, is produced as an intermediate in the uranium series by the emission of an α particle from thorium-230 (ionium); 226Ra emits α particles and gamma rays with a half-life of 1,599 years breaking down to 222Rn; chemically, it is an alkaline earth metal with properties similar to those of barium. Its therapeutic action is similar to that of x-rays, since the α emission is filtered out. [L. radius, ray]
* * *ra·di·um 'rād-ē-əm n, often attrib an intensely radioactive shining white metallic element that resembles barium chemically, that occurs in combination in minute quantities in minerals (as pitchblende or carnotite) principally as the isotope of mass number 226 formed from uranium 238, having a half-life of 1620 years, and emitting alpha particles and gamma rays to form radon, and that is used chiefly in luminous materials and in the treatment of cancer symbol Ra see ELEMENT (table)
* * *n.a radioactive metallic element that emits alpha and gamma rays during its decay into other elements. The gamma radiation was formerly employed in radiotherapy for the treatment of cancer. Because radon, a radioactive gas, is released from radium, the metal was enclosed in gas-tight containers during use. Radium is stored in lead-lined containers, which give protection from the radiation. Symbol: Ra.
* * *ra·di·um (raґde-əm) [from its radiant quality] a rare radioactive element in the uranium decay series. It has an atomic weight of 226, an atomic number of 88, and a half-life of 1600 years. It is found mainly in pitchblende and undergoes spontaneous disintegration with formation of a gas called radon (half-life = 3.85 days). In this process it emits alpha particles. Radon (alpha emitter) on deposit in solid form disintegrates into a series of decay products: radium A (half-life = 3 minutes), radium B (half-life = 26.7 minutes), and radium C (half-life = 19.5 minutes). The beta particles and gamma radiation used in clinical therapy originate from radium B and C. With radium in a sealed container and the same number of atoms of each decay product disintegrating per second, radium and its decay products are in equilibrium. In this state, the formation of beta particles and gamma rays reaches its maximum. In clinical gamma-ray therapy, shielding off of the beta particles can be accomplished by a metallic container, e.g., of gold or platinum. A glass-walled container permits irradiation with beta particles as well as gamma rays.
Medical dictionary. 2011.