قيادة

Lead is one of the oldest metals known to civilization. The uses of some of its alloys and salts have been documented early in history. The element derived its symbol Pb from the Latin word plumbium. The metal is rarely found in nature in its native form; however, it is found in several minerals, such as galena (PbS), anglesite (PbSO4), minium (Pb3O4) and cerussite (PbCO3). Its concentration in the earth’s crust is 12.5 mg/kg and in sea water 0.03mg/L.Lead has numerous applications as metal, alloys and compounds. The major applications of the metal and its alloys such as solder are as materials of construction for pipe lines, plumbing fixtures, wires, ammunition, containers for corrosive acids and shield against short-wavelength radiation. Another major application is in storage batteries in which both the metal and its dioxide are used. Several lead compounds, such as lead chromate (chrome yellow), lead sulfate (white lead), lead tetroxide (red lead), and the basic carbonate are used in paints.
Occurring naturally in the earth’s crust, lead is a heavy bluish-gray metal that is lustrous when freshly cut. It is rarely found as a pure metal but rather is complexed with other elements to form lead compounds. Found in ore with copper, zinc, and silver, lead is found in mineral form as galena (PbS), anglesite (PbSO4), and cerussite (PbCO3). It is easily malleable, smelted, and can be added to other metals to form alloys. Resistant to air and water corrosion, it does not mix easily with many solvents but will react with hot acids such as nitric and sulfuric. It has 4 naturally occurring isotopes as well as 17 that have been produced experimentally. Burning with a bluish-white flame, powdered lead displays pyrophoricity and releases toxic fumes when burned.