Question

In the case of alkali metal halides, the covalent character decreases in the order:

• A. $MF>MCl>MBr>MI$
• B. $MF>MCl>MI>MBr$
• C. $MI>MBr>MCl>MF$
• D. $MCl>MI>MBr>MF$

Answer 1

The correct option is C $MI>MBr>MCl>MF$

According to Fajan's rule:
Covalent character in an ionic compound is inversely proportional to the size of cation and directly propotional to the size of anion.
In the options, the cation is the same but the anions are different. Among the halides, the order of size is:
$F^{-}<C{l}^{-}<B{r}^{-}<I^{-}$
Therefore, the order of covalent character is:
$MI>MBr>MCl>MF$