Question

INCORRECT statements regarding defects in crystalline solids are :

a. Frenkel and Schottky defect are stoichiometric defects

b. Metal excess defect always cause decrease in density of the ionic solid and increase in its electrical conductivity

c.Metal deficiency defects always cause increase in density and electrical conductivity of the ionic solids

d. Impurity defects creates cationic vacancies in the ionic solids​

Answer 1

Explanation:

Defects or Imperfections in crystalline solid can be divided into four groups namely line defects, point defects, volume defects and surface defects. Historically, crystal point defects were first regarded in ionic crystals, not in metal crystals that were much simpler.

There are 3 types of point defects:

Stoichiometric defect

Frenkel defect

Schottky defect

1. Stoichiometric Defect:

In this kind of point defect, the ratio of positive and negative ions (Stoichiometric) and electrical neutrality of a solid is not disturbed. Sometimes it is also known as intrinsic or thermodynamic defects

Frenkel Defect:

In ionic solids generally, the smaller ion (cation) moves out of its place and occupies an intermolecular space. In this case, a vacancy defect is created on its original position and the interstitial defect is experienced at its new position.

Example: ZnS and AgCl

Schottky Defect

This kind of vacancy defects is found in Ionic Solids. But in ionic compounds, we need to balance the electrical neutrality of the compound so an equal number of anions and cations will be missing from the compound.

It reduces the density of the substance.