Question

The correct statement(s) regarding defects in solids is / are

• A. Frenkel defect is usually favoured by a very small difference in the sizes of cation and anion
• B. Frenkel defect is a dislocation defect
• C. trapping of an electron in the lattice leads to the formation of F-center
• D. Schottky defects have no effect on the physical properties of solid

Answer 1

Answer: (B), (C)

trapping of an electron in the lattice leads to the formation of F-center

$\Rightarrow$ Schottky Defect $\to$ Equal number of anions and cations are missing
No. of ions decreases, volume remains same $\Rightarrow$ Density decreases.
$\Rightarrow$ Frenkel Defect $\to$ If an ion is missing from lattice site and occupying interstitial site
Favoured in compounds : favoured in compounds in which there is large difference in size of cations and anions. with low coordination no.

$\Rightarrow$ F- centres $\Rightarrow$ Sites where anions are missing and instead electrons are present