Radium, a highly radioactive, brilliant-white metallic element that is produced by the natural disintegration of another element, uranium. The discovery of radium in 1898 was a landmark in the history of physics, for it stimulated further research into the nature of the atom.
Radium has been used in medicine as a source of radiation to treat certain types of malignant growths such as cancer. In industry, the radiation given off by radium can be used in examining materials for flaws by obtaining images like those obtained with X rays. Mixed with zinc sulfide, radium forms a luminous paint once used on the dials of watches, clocks, and other instruments. However, other radioisotopes have largely replaced radium for most purposes because they are cheaper to produce, easier to work with, and safer to use.
Radiation given off by radium either destroys living cells or injures them severely. This property makes radium extremely dangerous to handle, but it also accounts for radium's usefulness in the treatment of cancer. If ingested, radium will become deposited in the bones and, in time, will cause damage to body tissues.
Radium emits alpha particles, beta particles, and gamma rays. An alpha particle is the nucleus, or core, of a helium atom. A beta particle is an electron emitted from the nucleus of an atom. Gamma rays are similar to highly penetrating X rays. Radiation emitted by radium makes certain substances, such as diamonds and zinc sulfide, fluoresce (glow). The heat produced by the radiation makes radium a little warmer than its surroundings.
Radium has a half-life of 1,620 years (meaning that one ounce of radium is reduced by radioactive decay to one-half an ounce in 1,620 years). Radium decays to form radon, a radioactive gas. Radon decays to form another radioactive substance, which produces still another radioactive substance, and so on until finally lead is produced.
Radium is present in tiny amounts in seawater and in most of the earth's rocks. Its chief sources are pitchblende and other ores of its mother element, uranium. The principal sources have been mines in the Czech Republic, Canada, and Zaire.
The first steps in extracting radium from uranium ore are to crush the ore and dissolve it with sulfuric acid. This process yields a precipitate (solid residue) containing radium salts, barium salts, and other compounds. The precipitate is treated with carbonates, hydrochloric acid, and other chemicals to produce a solution of radium bromide and barium bromide. The radium bromide is concentrated by a process involving crystallization and filtration.
There has been little or no production of radium since the early 1960's. Although the total output of radium since its discovery has been only a few pounds, much of this is still in existence and is expected to fulfill all future demands.
Radium was discovered by Marie and Pierre Curie in Paris in 1898. Earlier that year they had discovered a new element, polonium, in pitchblende. Working with an assistant, G. Bmont, they then found that there was another, more radioactive, element in pitchblende—radium. They isolated a radium salt in December, 1898.
After years of arduous and dangerous labor, during which they processed tons of pitchblende, the Curies isolated 1/10 of a gram of radium chloride. Pure radium was not isolated until 1910, when Marie Curie obtained it from molten radium chloride.
The danger of radium radiation was not understood at first. In 1901, however, Henri Becquerel suffered a burn from carrying a piece of radium salt in his watch pocket. Pierre Curie then deliberately burned himself to learn the effects of radium on the body. His report immediately suggested to doctors that radium, by destroying cells, might be useful in the treatment of cancer.
Symbol: Ra. Atomic number: 88. Atomic weight: 226.0254. Melting point: 1,292. (700C). Specific gravity: 5. Valence: +2. Half-life: 1,620 years. Radium belongs to Group IIA of the Periodic Table.