Question

explane impurity defect in crystalline solid

Answer 1

A point defect can be an atom missing from a site of a Crystal or an impurity atom that occupies either a normal lattice site or a hole in a lattice between atoms. .......
A Frenkel defeat is an ion that occupies an incorrect site in the lattice.

Answer 2

a point defect can be an atom missing from a site in the crystal ( a vacancy) or an impurity atoms that occupies either a normal lattice site( a substitutional impurity) or a hole in the lattice between atoms ( an interstitial impurity)..
A Frenkel defect is an ion that occupies an incorrect site in the lattice.