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History and Production
The word lead is Anglo-Saxon while in Latin it is called plumbum. Long known since prehistoric times. It was used in ancient Egypt for glazing pottery since at least 5000 BC. The Romans used lead for water pipes and plumbing. The metal is obtained by roasting galena (PbS) in air to give PgO which is then reduced with coke in a blast furnace. It is further purified by electrolytic refinement method. This yield lead (at cathode) with purity grade of 99.99%. Zone-refining method can be used to obtain a much purer form of the metal.
The metal is mainly used as alloys such as in storage batteries (91% Pb, 9% Sb). With tin in making organ pipes, solders and bearing metals. It is also used in ammunition and weights. Lead is also used as a radiation shield for X-ray equipment and nuclear reactors. It is also used to make rusting-inhibiting paints such as read lead oxide (Pb3O4) and yellow chromate (PbCrO4). Recently, the use of the lead compound (tetraethyl) as an 'anti-knock'
agent in gasoline is diminishing especially in countries with strict environmental lagislation.
Physical Data
It is a bluish-grey metal of bright luster, soft, ductile and very malleable. It is a poor conductor of electricity but very resistant to corrosion. The metal has a natural abundance of about 13 ppm. It is rarely distributed as native but is usually found in minerals such as galena (left), anglesite (PbSO4) and cerussite (PbCO3) etc.
Interatomic distance: 350.0 pm
Melting point: 327.46°C
Boiling point: 1749°C
Thermal conductivity/Wm-1K-1: 35.3 (27°C)
Density/kgm-3: 11350 (20°C), 10678 (m.p.)
Standard Thermodynamic Data (atomic gas)
Enthalpy of formation: 195.2 kJ/mol
Gibbs free energy of formation: 162.2 kJ/mol
Entropy: 175.4 J/mol K
Heat capacity: 20.8 J/mol K
Electronic data
Electronic configuration: [Xe] 4f14 5d10 6s2 6p2
Term symbol: 3P0
Electron affinity: 35.1207 kJ/mol Electronegativity (Pauline): 1.80
Ionization energy (first, second, third): 715.599, 1450.39, 3081.48 kJ/mol
Chemical properties
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