Introduction Lead is a rare element present in the earth’s crust in a 1.4 Â 10À3% (w/w). It is a toxic heavy metal that exists only in a cubic close-packed metallic form. It shows the preference for the divalent state with electronic configuration [Xe]4f145d106s2 and low stability of the Pb–Pb covalent bond. Lead(IV) in solution is unstable (electronic configuration: [Xe]4f145d10). The most important Pb ore is galena (PbS). Other lead ores are anglesite (PbSO4), cerussite (PbCO3), mimetesite (Pb5(AsO4)3Cl), and pyromorphite (Pb5(PO4)3Cl).