Question

Which of the following solids will show the given crystal lattice defect?

• A. $NaCl$
• B. $AgBr$
• C. $AgCl$
• D. $KCl$

Answer 1

Answer: (B), (C)

$AgCl$

In the given crystal lattice, cation $A^{+}$ has left its lattice site and occupies a position at interstitial site.
Also, the charge is neutral since the $A^{+}$ does not left the lattice.
Here, $A^{+}$ ion is only delocalised to the interstitial site. Hence, it shows Frenkel defects.

Frenkel defect is shown by those in which there is large difference in the size of cations and anions.
Among the give salts, the size of $A{g}^{+}$ ion is so small, thus it has larger difference with size of $C{l}^{-}$ and $B{r}^{-}$.
Hence, (b) and (c) shows Frenkel defects.