Lead
Lead (/lɛd/) is a chemical element in the carbon group with symbol Pb (from Latin: plumbum) and atomic number 82. Lead is a soft, malleable and heavy post-transition metal. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishesto a dull grayish color when exposed to air. Lead has a shiny chrome-silver luster when it is melted into a liquid. It is also the heaviest non-radioactive element.
Lead is used in building construction, lead-acid batteries, bullets and shot, weights, as part of solders, pewters, fusible alloys, and as a radiation shield. Lead has the highest atomic number of all of the stable elements, although the next higher element,bismuth, has one isotope with a half-life that is so long (over one billion times the estimated age of the universe) that it can be considered stable. Lead's four stable isotopes have 82 protons, a magic number in the nuclear shell model of atomic nuclei. The isotope lead-208 also has 126 neutrons, another magic number, and is hence double magic, a property that grants it enhanced stability: lead-208 is the heaviest known stable isotope.
If ingested, lead is poisonous to animals and humans, damaging the nervous system and causing brain disorders. Excessive lead also causes blood disorders in mammals. Lead is a neurotoxin that accumulates both in soft tissues and the bones. Lead poisoning has been documented from ancient Rome, ancient Greece, and ancient China.
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Lead, a plentiful by-product of the ancient silver smelting process, was produced in the Roman Empire with an estimated peak production of 80,000 metric tons per year – a truly industrial scale.[3] The metal was used along with other materials in the vast water supply network of the Romans for the manufacture of water pipes, particularly for urban plumbing.[4]...
Lead has been commonly used for thousands of years because it is widespread, easy to extract and easy to work with. It is highly malleable as well as easy to smelt. Metallic lead beads dating back to 6400 BCE have been found in Çatalhöyük in modern-day Turkey.[33] In the early Bronze Age, lead was used with antimony and arsenic.[34]
The largest preindustrial producer of lead was the Roman economy, with an estimated annual output of 80,000 tonnes, which was typically won as a by-product of extensive silver smelting.[32][35][36] Roman mining activities occurred in Central Europe, Roman Britain, the Balkans,Greece, Asia Minor and Hispania which alone accounted for 40% of world production.[32]
Roman lead pipes often bore the insignia of Roman emperors (see Roman lead pipe inscriptions). Lead plumbing in the Latin West may have been continued beyond the age of Theoderic the Great into the medieval period.[37] Many Roman "pigs" (ingots) of lead figure in Derbyshire lead mining history and in the history of the industry in other English centers. The Romans also used lead in molten form to secure iron pins that held together large limestone blocks in certain monumental buildings.[38] In alchemy, lead was thought to be the oldest metal and was associated with the planet Saturn. Alchemists accordingly used Saturn's symbol (the scythe, ♄) to refer to lead.[39]
Up to the 17th century, tin was often not distinguished from lead: lead was called plumbum nigrum (literally, "black lead"), while tin was called plumbum candidum (literally, "bright lead").[40] Their inherence through history can also be seen in other languages: the word "ołów" in Polish and "olovo" in Czech mean lead, but in Russian the cognate "олово" (olovo) means tin.[41] Lead's symbol Pb is an abbreviation of its Latin name plumbum for soft metals; the English words "plumbing", "plumber", "plumb", and "plumb-bob" also derive from this Latin root.[42]
http://en.wikipedia.org/wiki/Lead
http://en.wikipedia.org/wiki/Tetraethyllead