A crystal is made up of metal ions 'M₁' and 'M₂'
and oxide ions. Oxide ions form a ccp lattice
structure. The cation 'M₁' occupies 50% of
octahedral voids and the cation 'M₂' occupies
12.5% of tetrahedral voids of oxide lattice. The
oxidation numbers of 'M₁' and 'M₂' are,
respectively :