Radium Industrial Applications and Uses
Radium ,chemical symbol Ra, atomic number 88, and relative atomic mass [226] for the longest-life isotope, is the heaviest element of the alkaline-earth metals. The name Alkaline-Earth Metals 265 4 Less Common Nonferrous Metals comes from the Latin radius, ray, owing to its radioactivity. The pure metal is brilliant white when freshly prepared but tarnishes on exposure to air, probably due to the formation of nitride. It exhibits luminescence, as do its salts; it decomposes in water and is somewhat more volatile than barium. Radium imparts a carmine red color to a flame of a Bunsen gas burner. Radium emits alpha, beta, and gamma rays and, when mixed with beryllium, produces neutrons according to the nuclear reaction 9Be(α,n)12C. Twenty-five isotopes are now known, including radium-226, the most common isotope, which has a half-life of 1620 years. Radium loses about 1% of its activity in 25 years, being transformed into elements of lower atomic weight. Lead-206 is the final prproduct of disintegration. Stored radium should be ventilated to prevent buildup of radon.
Radium was discovered in 1898 by Marie Curie and Pierre Curie. They managed to extract 1 mg of radium from ten tonnes of the uranium ore pitchblende (uranium oxide, U3O8), a considerable feat, given the chemically methods of separation available to them. They identified that it was a new element because its atomic spectrum revealed new lines. Their samples glowed with a faint blue light in the dark, caused by the intense radioactivity exciting the surrounding air.
The metal itself was isolated by Marie Curie and André Debierne in 1911, by means of the electrolysis of radium chloride. At Debierne’s suggestion, they used a mercury cathode in which the liberated radium dissolved. This was then heated to distil off the mercury leaving the radium behind.
Natural abundance
Radium is present in all uranium ores, and could be extracted as a by-product of uranium refining. Uranium ores from DR Congo and Canada are richest in radium. Today radium is extracted from spent fuel rods from nuclear reactors. Annual production of this element is fewer than 100 grams per year.
Biological role
Radium has no known biological role. It is toxic due to its radioactivity.
Industrial Applications and Uses
Radium now has few uses, because it is so highly radioactive.
Radium-223 is sometimes used to treat prostate cancer that has spread to the bones. Because bones contain calcium and radium is in the same group as calcium, it can be used to target cancerous bone cells. It gives off alpha particles that can kill the cancerous cells.
Radium used to be used in luminous paints, for example in clock and watch dials. Although the alpha rays could not pass through the glass or metal of the watch casing, it is now considered to be too hazardous to be used in this way.
At the beginning of the 20th century, radium was used to establish the standard prototype of the curie. Actually, one curie is exactly equal to the radioactivity of a source that has the same radioactivity as 1 g of the radionuclide radium-226 in secular equilibrium with its derivative, radon-222 (or emanation).37 In spite of the new mandatory SI unit of radioactivity, the becquerel, symbol Bq, the curie, Ci, is sometimes still in use (1 Ci = 37 GBq). Twenty-five isotopes are now known; radium-226, the most common isotope, has a half-life of 1620 years. This isotope is purged from radium and sealed in minute tubes, which are used in the treatment of cancer and other diseases. Radium is used in the production of self-luminous paints, neutron sources, and in medicine for the treatment of disease. Some of the more recently discovered radioisotopes, such as 60Co or 137Cs, are now being used in place of radium. Some of these sources are much more powerful, and others are safer to use. Inhalation, injection, or body exposure to radium can cause cancer and other bodily disorders. The maximum permissible burden in the total body for 226Ra is 7.4 kBq.
Processing and Industrial
Preparation Radium is obtained commercially as bromide and chloride; it is doubtful if any appreciable stock of the isolated element now exists.
