Question

Which of the following is the most covalent halide?

• A. $Al{F}_3$
• B. $AlB{r}_3$
• C. $AlC{l}_3$
• D. $Al{I}_3$

Answer 1

The correct option is D $Al{I}_3$

Compound	Anion
$Al{F}_3$	$F^{-}$
$AlC{l}_3$	$C{l}^{-}$
$AlB{r}_3$	$B{r}^{-}$
$Al{I}_3$	$I^{-}$

Since $I^{-}$ is largest in size, it has the highest polarizability as well. So, the most covalent halide is $Al{I}_3$ (since, the cation is the same, i.e., $A{l}^{3+}$ for all, thus we do not have to consider the impact of cation on polarization).
Therefore, option (d) is the correct answer.