Lead(II) oxide is the chemical compound with the formula PbO. Lead(II) oxide occurs in two forms: red, having a tetragonal crystal structure and
yellow, having an orthorhombic crystal structure. Both forms occur naturally as minerals: the red form is known as litharge and the yellow form is known as massicot.
Preparation and structure
PbO is prepared by heating lead metal in air at 600 C. Alternatively, it is obtained by the thermal decomposition of lead(II) nitrate or lead carbonate:
- 2Pb(NO3)2) → 2PbO + 4NO2 + O2
- PbCO3 → PbO + CO2
The structure of the solid, determined by X-ray crystallography, reveals a pyramidal four-coordinate Pb center. The pyramidal nature indicates the presence of a stereochemically active lone pair of electrons.
Reactions
The red and yellow forms of this material are related by a small change in enthalpy: PbO(red) → PbO(yellow) ΔH = 1.6 kJ/mol
PbO is amphoteric, which means that it reacts with both acids and with bases. With acids, it forms salts of Pb
2+ via the intermediacy of oxo clusters such as [Pb
6O(OH)
6]
4+. With strong base, PbO dissolves to form plumbite(II) salts: PbO + H
2O + OH
- → [Pb(OH)
3]
-
