Elemental Lead, General Inorganic Chemistry

Lead is the most massive of the Group IV B elements, which include carbon, sili-can, germanium, and tin. As with other elements in its row, the electronic structure of lead is expressed in a filled configuration of xenon, plus the additional partially filled subsheils, i.e., [Xe] 4f 5d 6S 6p. The physical properties of elemental lead are listed in Table 3. 

The inorganic chemistry of lead is dominated by the divalent (2 ) oxidation state rather than the tetravalent (4 ) oxidation state. The divalent state is more dominant in Group IV B elements as the atomic number increases. Dominance of the divalent state occurs because, within Group IV B, there is a decrease in single bond strength with increasing atomic number [13]. 

The average energy of a C-H bond is 100 kcal/mole it is this factor that allows CH4 to be more stable than CH2. For lead, the Pb-H bond energy is only about 65 kcal/mole. This energy is too small to compensate for the Pb(II) Pb(IV) promotional energy therefore, PbX2 compounds are more stable. 

As with Si, Ge, and Sn, lead does not form qk multiple bonds either with itself or with other elements [13]. This accounts for the lack of lead analogs for the numerous classes of organic compounds. 

Atomic weight Atomic number Oxidation states Density Melting point Boiling point 

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In general, the chemistry of inorganic lead compounds is similar to that of the alkaline-earth elements. Thus the carbonate, nitrate, and sulfate of lead are isomorphous with the corresponding compounds of calcium, barium, and strontium. In addition, many inorganic lead compounds possess two or more crystalline forms having different properties. For example, the oxides and the sulfide of bivalent lead are frequendy colored as a result of their state of crystallisation. Pure, tetragonal a-PbO is red pure, orthorhombic P PbO is yeUow and crystals of lead sulfide, PbS, have a black, metallic luster. 

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