Lead Metal and Alloys
Lead is a soft, malleable and ductile metal. It has an abundance in the earth's crust of 14 ppm. In its elemental form, lead has a metallic gray appearance. Lead occurs naturally as a mixture of four stable isotopes: 204Pb (1.48%), 206Pb (23.6%), 207Pb (22.6%), and 208Pb (52.3%). 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. , the main source of the metal being the ore "galena", lead (II) sulphide (PbS) which occurs as grey cubic crystals, often in conjunction with "sphalerite", the equivalent sulphide of zinc. Lead oxidises readily in moist air, is stable to oxygen and water, but dissolves in nitric acid.
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