Lead Information
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Lead Element
Lead is a chemical element with the symbol Pb (from the Latin
plumbum) and atomic number 82. It is a heavy metal that is denser than most
common materials. Lead is soft and malleable, and also has a relatively low
melting point. When freshly cut, lead is silvery with a hint of blue; it
tarnishes to a dull gray color when exposed to air. Lead has the highest atomic
number of any stable element and three of its isotopes are endpoints of major
nuclear decay chains of heavier elements.
Lead is a relatively unreactive post-transition metal. Its weak
metallic character is illustrated by its amphoteric nature; lead and lead
oxides react with acids and bases, and it tends to form covalent bonds.
Compounds of lead are usually found in the +2 oxidation state rather than the
+4 state common with lighter members of the carbon group. Exceptions are mostly
limited to organolead compounds. Like the lighter members of the group, lead
tends to bond with itself; it can form chains and polyhedral structures.
Lead is easily extracted from its ores; prehistoric people in
Western Asia knew of it. Galena, a principal ore of lead, often bears silver,
interest in which helped initiate widespread extraction and use of lead in
ancient Rome. Lead production declined after the fall of Rome and did not reach
comparable levels until the Industrial Revolution. In 2014, the annual global
production of lead was about ten million tonnes, over half of which was from
recycling. Lead's high density, low melting point, ductility and relative
inertness to oxidation make it useful. These properties, combined with its
relative abundance and low cost, resulted in its extensive use in construction,
plumbing, batteries, bullets and shot, weights, solders, pewters, fusible
alloys, white paints, leaded gasoline, and radiation shielding.
Although lead is not abundant, natural concentration processes
have resulted in substantial deposits of commercial significance, particularly
in the United States but also in Canada, Australia, Spain, Germany, Africa, and
South America. Significant deposits are found in the United States in the
western states and the Mississippi valley. Rarely found free in nature, lead is
present in several minerals, but all are of minor significance except the
sulfide, PbS (galena, or lead glance), which is the major source of lead
production throughout the world. Lead is also found in anglesite (PbSO4) and
cerussite (PbCO3). By the early 21st century, China, Australia, the United
States, Peru, Mexico, and India were the world’s top producers of lead in
concentrate.
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