Which of the following crystals exhibits Schottky defect?

Options

A. `NaCl`
B. `CsCl`
C. `AgBr`
D. All of these

Answer

4

Explanation

When an ion (cation or anion) is missing form its normal lattice site,a lattice vacancy (Schottky defect) is created. In stoichiometric crystals a vacancy of one ion has to be accompanied by the vacancy of the oppositely charged ion in order to maintain electrical neutraility.
Schottky defeat is slowly by highly ionic compounds which have
`1` high coordination number and
`2` small difference in the size of cations and anions.
Thus, there might be an equal number of sodium ion vacancies and chloride ion vacancies in a `NaCl` crystal.