SiO2

MgO

SO2(s)

CrO2

molecule

ion

electron

atom

conducting solid

network solid

covalent solid

ionic solid

Frenkel defect

Schottky defect

Vacancy defect

Metal deficiency defect

some cations move from their lattice site to interstitial sites.

equal number of cations and anions are missing from the lattice.

some lattice sites are occupied by electrons.

some impurity is present in the lattice.