Radium
. Radium (Latin radius,”ray”), symbol Ra, chemically reactive, silvery white, radioactive metallic element. In group 2 (or IIa) of the periodic table (see Periodic Law ), radium is one of the alkaline earth metals . The atomic number of radium is 88. Radium was discovered in the ore pitchblende by the French chemists Marie Curie and Pierre Curie in 1898. They discovered that the ore was more radioactive than its principal component, uranium , and they separated the ore into many chemical fractions in order to isolate the unknown sources of radioactivity . One fraction, isolated by use of bismuth sulfide, contained a strongly radioactive substance that the Curies showed was a new element, polonium . A highly radioactive barium-chloride fraction was treated to remove the radioactive substance, which was discovered to be a new element, radium. PROPERTIES AND OCCURRENCE Radium-226 metal melts at about 700° C (about 1292° F), and has a specific gravity of 5.5. The element oxidizes immedia