Which is the most covalent?

Which is the most covalent?
  1. $\mathrm{AlCl}_3$
  2. $\mathrm{AlI}_3$
  3. $\mathrm{MgI}_2$
  4. $\mathrm{NaI}$

Solution

$\mathrm{AlI}_3$ is the most covalent compound. According to Fajan's rule, covalent character $\propto$ small cation or large anion or positive charge Since, lesser the electronegativity difference more covalent is aluminium halide. Hence, the most covalent halide is $\mathrm{AlI}_3$.

Asked in: AP EAMCET 2021 (24 Aug Shift 1)

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