Radium Facts and Chemical and Physical Properties

Radium Facts and Chemical and Physical Properties Atomic Number: 88 Symbol: Ra Atomic Weight: 226.0254 Electron Configuration: [Rn] 7s2 Word Origin: Latin radius: ray Element Classification: alkaline earth metal Discovery It was discovered by Pierre and Marie Curie in 1898 (France/Poland). It was isolated in 1911 by Mme. Curie and Debierne. Isotopes Sixteen isotopes of radium are known. The most common isotope is Ra-226, which has a half-life of 1620 years. Properties Radium is an alkaline earth metal. Radium has a melting point of 700Â °C, boiling point of 1140Â °C, specific gravity estimated to be 5, and valence of 2. Pure radium metal is bright white when freshly prepared, although it blackens upon exposure to air. The element decomposes in water. It is somewhat more volatile than the element barium. Radium and its salts exhibit luminescence and impart a carmine color to flame. Radium emits alpha, beta, and gamma rays. It produces neutrons when mixed with beryllium. A single gram of Ra-226 decays at the rate of 3.7x1010 disintegrations per second. [The curie (Ci) is defined to be the quantity of radioactivity which has the same rate of disintegration as 1 gram of Ra-226.] A gram of radium produces around 0.0001 ml (STP) of radon gas (emanation) per day and about 1000 calories per year. Radium loses about 1% of its activity over 25 years, with lead as its final disintegration product. Radium is a radiological hazard. Stored radium requires ven tilation to prevent the build-up of radon gas. Uses Radium has been used to produce neutron sources, luminous paints, and medical radioisotopes. Sources Radium was discovered in pitchblende or uraninite. Radium is found in all uranium minerals. There is approximately 1 gram of radium for each 7 tons of pitchblende. Radium was first isolated by electrolysis of a radium chloride solution, using a mercury cathode. The resulting amalgam yielded pure radium metal upon distillation in hydrogen. Radium is commercially obtained as its chloride or bromide and tends not to be purified as an element. Physical Data Density (g/cc): (5.5) Melting Point (K): 973 Boiling Point (K): 1413 Appearance: silvery white, radioactive element Atomic Volume (cc/mol): 45.0 Ionic Radius: 143 (2e) Specific Heat (20Â °C J/g mol): 0.120 Fusion Heat (kJ/mol): (9.6) Evaporation Heat (kJ/mol): (113) Pauling Negativity Number: 0.9 First Ionizing Energy (kJ/mol): 509.0 Oxidation States: 2 Sources CRC Handbook of Chemistry Physics, 18th Ed.Crescent Chemical Company, 2001.Langes Handbook of Chemistry, 1952.Los Alamos National Laboratory, 2001.