Question

The type of defect involves an atom from an impurity substituting for a lattice atom is

• A. Interstitial defect
• B. Vacancy defect
• C. Substitutional defect
• D. Frenkel defect

Hint:

Point Defects. Vacancy (missing atom), Interstitial (extra atom between sites), Substitutional (impurity atom replaces host atom). Frenkel/Schottky are specific to ionic crystals.

Answer 1

The Correct Option is C

Point defects are imperfections involving one or two atomic positions in a crystal lattice.
- Vacancy defect: An atom is missing from its normal lattice site.
- Interstitial defect: An atom (either of the host material or an impurity) occupies a position between normal lattice sites (an interstitial site).
- Substitutional defect: An impurity atom replaces or substitutes for a host atom at a normal lattice site.
This is described in the question.
- Frenkel defect (in ionic crystals): A cation leaves its normal lattice site and occupies an interstitial site, creating a vacancy and an interstitial defect simultaneously.
- Schottky defect (in ionic crystals): A pair of cation and anion vacancies.
The defect involving an impurity atom substituting for a host lattice atom is a substitutional defect.