Lead is a lustrous, silvery metal that tarnishes in the presence of air and becomes a dull bluish gray. Soft and malleable, it has a low melting point (327 degrees Celcius). It's chemical symbol, Pb is derived from plumbum, the Latin word for waterworks, because of lead's extensive use in ancient water pipes. Its atomic number is 82; its atomic weight is 207.19.
The Earth's crust is about 15 ppm lead. Four Stable lead isotopes exist in nature; three of them are end products of the radioactive decay of Uranium and Thorium. It is assumed that all of the fourth isotope that exists in rocks has been there since the rockes were formed. The most valuable lead ore is galena, which is almost always mixed with other valuable ores. The production of pure lead from ores is a complex process in which the raw material undergoes several purifications. Much of the world production of bismuth, arsenic, antimony, and silver comes from the production of lead. Lead is also recycled from scrap metal.
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