Question

Which of the following statements is incorrect regarding the defects in solids?

• A. Doping in crystal introduces dislocation defect
• B. $AgBr$ crystal shows both Schottky and Frenkel defect
• C. Metal excess defect can occur with extra cation present in the interstitial voids
• D. Solids containing F-centers are paramagnetic
  

Answer 1

The correct option is A Doping in crystal introduces dislocation defect

$AgBr$ shows both, Frenkel as well as Schottky defects.
Thus, statement (a) is correct.

F-centers are vacant sites of crystal lattice, which are occupied by electrons and can cause the compound to appear coloured. Solids containing F-centers are paramagnetic, as the electrons occupying the vacant sites are unpaired.
Thus, statement (b) is correct.

Doping a different valency element may either result in a free electron or positive hole. It does not make ions to move away from their lattice sites and occupy interstitial positions
So, statement (c) is incorrect.

On heating ZnO, it loses oxygen and some of $Z{n}^{2+}$ occupy interstitial sites. This is the example of a metal excess defect. So metal excess defect can occur with an extra cation present in an interstitial site.
So, statement (d) is correct.