Question

Schottky defect in solids is due to:
A.A pair of cation and anion vacancies.
B.Occupation of interstitial site by a pair of cation and anion.
C.Occupation of interstitial site by a cation.
D.Occupation of interstitial site by an anion.

Answer 1

Hint: When a lattice is formed , the formation takes place rapidly which results in some defects in a solid. These defects are categorized on the basis of the movement of anions and cations of the lattice and the valencies created by them.

Complete step by step answer:
As we all know that the solids are formed from a large number of particles, when these particles participate they combine with each other rapidly which results in some defects to the solid.
These defects are classified as stoichiometric, non-stoichiometric and impurity defects. The defects in which the stoichiometry is not disturbed are known as stoichiometric defects while the defects in which the stoichiometry of the solid is disturbed are known as non-stoichiometric defects.
The three defects are seen under the category of stoichiometric defect.
Frenkel defect: The defect in which the cations leave their positions and enter into interstitial sites of lattice. The defect is seen in the solids or substances having low coordination numbers.
Impurity defect: When some substances are heated, cations leave their position from lattice and to neutralize that lattice an another cation takes place of that older cation in the lattice and hence creates impurity in the lattice therefore it is known as impurity defect.
Schottky defect: When the same number of cations and anions leave the lattice due to some reasons and they create vacancies but the lattice remains neutral and thus results in schottky defect. So we can say that schottky defect in solids is due to a pair of cation and anion valencies.
Hence option (A) is correct.

Note:
The schottky defect is a part of stoichiometric defects because the number of cations and anions which leave the lattice are equal in number and this helps in maintaining the stoichiometry of the solid, but due to the valencies left behind this is termed as defect.