Question

Which of the following combinations of ions will have the highest polarisation?

• A. $F{e}^{2+},B{r}^{-}$
• B. $N{i}^{4+},B{r}^{-}$
• C. $N{i}^{2+},B{r}^{-}$
• D. $Fe,B{r}^{-}$

Answer 1

The correct option is B $N{i}^{4+},B{r}^{-}$

According to fajan's rule, more the polarization of an anion by the cation, more will be the covalent character in the ionic bond. For maximum polarization of the anion by the cation, size of cation should be small and size of anion should be large. Also, more the charge on cation more the polarisation of anion.
$\left(N{i}^{4+}\right)$ has highest charge which increases the polarising power of the cation and thus increases the polarisation of $B{r}^{-}$ ion.