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 Uranium (U)is a silvery-white, radioactive metal. It is more plentiful than such "common" elements as iodine, mercury, and silver, but only tiny amounts of uranium are present in most of the rocks in which it is found. Uranium was discovered in 1789 by the German chemist Martin H. Klaproth, who found it in pitchblende, a dark bluish-black mineral. Klaproth named the element in honor of the planet Uranus, which had been discovered eight years earlier. In 1841, pure uranium was isolated from the other elements in pitchblende by the French chemist Eugène Péligot. Properties Uranium belongs to the Actinide Series of elements. With an atomic weight of 238.03, it is the heaviest natural element. It has the atomic number 92. It melts at 1132º C and boils at 3818º C. Uranium is highly reactive, and it combines with most other elements to form chemical compounds. These compounds are always extremely poisonous. All isotopes of uranium are radioactive. Sources Many rocks contain bits of uranium, but large amounts occur only in such minerals as pitchblende and carnotite. Pitchblende, which contains various uranium oxides, is the richest uranium ore. Carnotite is the most important uranium ore mined in the United States. It consists of uranium, oxygen, potassium, and vanadium. Uranium also occurs in seawater, and could be recovered from the oceans if prices rose significantly. The United States produces more uranium oxide than any other country, followed by Canada and South Africa. The chief deposits of uranium ore in the United States are in Wyoming, New Mexico, Texas, Colorado, and Utah, in that order. About 85 per cent of Canada's uranium comes from the province of Ontario. Much of South Africa's uranium is a by-product of gold mining. The gold mines in the Witwatersrand area, near Johannesburg, provide large amounts of uranium.
Uses Uranium and its compounds have been used for various purposes for more than 2,000 years. Colored glass produced about A.D. 79 contains uranium oxide, and this substance has been used through the centuries to color glass. For nearly 100 years after the discovery of uranium it continued to be used chiefly as a pigment in glass manufacturing. It was also used as a pigment in painting china and as a chemical for processing photographs. In 1896, the French physicist Antoine Henri Becquerel discovered that uranium is radioactive. In 1938, the German chemists Otto Hahn and Fritz Strassman used uranium to produce the first artificial nuclear fission. In 1942, the Italian-born physicist Enrico Fermi and his co-workers at the University of Chicago produced the first artificial nuclear chain reaction, using uranium as the fissionable material. Today, uranium is used chiefly as a fuel for nuclear reactors, which in turn produce electricity. About 1 pound of uranium produces as much energy as 3 million pounds of coal. Uranium is also used in making atomic bombs and some other nuclear weapons. Medical researchers use uranium to produce radiation for certain experiments. In addition, uranium is used in scientific research to produce various radioactive isotopes and such artificial elements as neptunium and plutonium. The high density of uranium means that it also finds uses in the keels of yachts and as counterweights for aircraft control surfaces, as well as for radiation shielding.
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ROBINSON LIBRARY --> Science. --> Chemistry. --> Chemical Elements. This page was last updated on 08/31/2011. |
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Uranium
near the earth's surface is mined by a process called strip
mining. Huge power shovels remove the rocks and soil
that cover the deposits, and smaller shovels then dig out
the uranium ore. Miners use explosives and drills to
excavate uranium ore that lies deep below the ground.
The
uranium ore is taken from the mine to a uranium-concentrating
plant, where sulfuric acid is used to extract an
oxide of uranium called yellowcake. The
yellowcake is then combined with fluorine to produce
uranium hexafluoride, which is subsequently refined into
pure uranium.
