Question

Schottky defect is observed in crystals when ________.

• A. equal number of cations and anions are missing from the lattice.
• B. some lattice sites are occupied by electrons.
• C. some cations move from their lattice site to interstitial sites
• D. some impurity is present in the lattice.

Answer 1

The correct option is A equal number of cations and anions are missing from the lattice.

Schottky defect in ionic crystals arises when equal number of cations and anions are missing from the normal site of the lattice, resulting in an equal number of cation and anion vacancies.

This defect occurs when cations and anions are of similar size.

Hence, the correct answer is option $\left(B\right).$