Select the incorrect statement.

For $NaCl$,the number of Schottky pairs per $cm^3$ at room temperature is

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 solids.

$A$ silicon specimen is made into a $p-$type semiconductor by doping,on an average,one indium atom per $5 \times 10^7$ silicon atoms. If the number density of atoms in the silicon specimen is $5 \times 10^{28} \ \text{atoms} \ m^{-3}$,then the number of acceptor atoms in silicon per cubic centimeter will be

Which relationship is correct regarding the coordination number and the size of cations and anions in ionic compounds exhibiting Schottky defect?

Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it.