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Atomic Number: 82
Atomic Symbol: Pb
Atomic Weight: 207.2
Electron Configuration: [Xe]6s24f145d106p2
History
(Anglo-Saxon lead; L. plumbum) Long known, mentioned in Exodus. The
alchemists believed lead to be the oldest metal and associated with the planet
Saturn. Native lead occurs in nature, but it is rare.
Sources
Lead is obtained chiefly from galena (PbS) by a roasting process.
Anglesite, cerussite, and minim are other common lead minerals.
Properties
Lead is a bluish-white metal of bright luster, is very soft, highly
malleable, ductile, and a poor conductor of electricity. It is very resistant to
corrosion; lead pipes bearing the insignia of Roman emperors, used as drains
from the baths, are still in service. It is used in containers for corrosive
liquids (such as sulfuric acid) and may be toughened by the addition of a small
percentage of antimony or other metals.
Forms
Natural lead is a mixture of four stable isotopes: 204Pb
(1.48%), 206Pb (23.6%), 207Pb (22.6%), and 208Pb
(52.3%). Lead isotopes are the end products of each of the three series of
naturally occurring radioactive elements: 206Pb for the uranium
series, 207Pb for the actinium series, and 208Pb for the
thorium series. Twenty seven other isotopes of lead, all of which are
radioactive, are recognized.
Its alloys include solder, type metal, and various antifriction
metals. Great quantities of lead, both as the metal and as the dioxide, are used
in storage batteries. Much metal also goes into cable covering, plumbing,
ammunition, and in the manufacture of lead tetraethyl.
Uses
The metal is very effective as a sound absorber, is used as a
radiation shield around X-ray equipment and nuclear reactors, and is used to
absorb vibration. White lead, the basic carbonate, sublimed white lead, chrome
yellow, and other lead compounds are used extensively in paints, although in
recent years the use of lead in paints has been drastically curtailed to
eliminate or reduce health hazards.
Lead oxide is used in producing fine "crystal glass" and "flint
glass" of a high index of refraction for achromatic lenses. The nitrate and the
acetate are soluble salts. Lead salts such as lead arsenate have been used as
insecticides, but their use in recent years has been practically eliminated in
favor of less harmful organic compounds.
Handling
Care must be used in handling lead as it is a cumulative poison.
Environmental concerns with lead poisoning has resulted in a national program to
eliminate the lead in gasoline.
Sources: CRC Handbook of Chemistry and
Physics and the American Chemical Society.
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