Question

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

• A. $AgBr$
• B. Both (b) and (c)
• C. $NaCl$
• D. $AgCl$

Answer 1

The correct option is B Both (b) and (c)

In the given crystal lattice, cation $A^{+}$ has left its lattice site and occupied a position at interstitial site.
Also, the crystal stays neutral since $A^{+}$ does not leave 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 quite small so the difference between sizes of $C{l}^{-}$ and $B{r}^{-}$ is large.
Hence, (b) and (c) show Frenkel defects.