Question

Ionic solids, with Schottky defects, contain in their structure
A) Equal number of cation and anion vacancies
B) Anion vacancies and interstitial anions
C) Cation vacancies only
D) Cation vacancies and interstitial cations

Answer 1

Hint: The various defects in crystal lattice arises due to the missing of cation and anion from the crystals which causes vacant sites. In some defects cation causes vacancy, in some anion causes vacancy and in some cases both the cation and anion causes vacancy.

Complete Step by Step Answer:
In Schottky defect the equal number of anions and cations are removed from the crystal lattice to produce vacancy in the crystal which in turns causes defect in the crystal.

In this defect at first one cation is removed from the crystal solid. Now to maintain the neutrality of the crystal lattice an anion is also removed from the crystal lattice.

The major characteristic of Schottky defect are:
- In this defect there is a very small difference in size between cation and anion.
- In this defect both the Cation and anion leave the solid crystal.
- Atoms or the ions move out of the crystal permanently in this defect.
- Here generally two vacancies are formed, one for cation and another one is for the anion.
- The density of the solid decreases.
Thus the correct option is C.

Note: The crystal solid like sodium chloride, silver bromide, potassium chloride, potassium bromide show schottky defect by the removal of corresponding cation and anions. Due to schottky defects the crystal lattice gives colour.