Question

Which of the following has covalent bond?

• A. $N{{a}_{2}}S$
• B. $AlC{{l}_{3}}$
• C. $NaH$
• D. $MgC{{l}_{2}}$

Answer 1

Answer: (B)

$AlC{{l}_{3}}$

Answer 2

We know that $A{{l}^{3+}}$ cation is smaller than $N{{a}^{+}}$ (because of greater nuclear charge). According to Fajans rule, small cation polarise anion upto greater extent. Hence, $A{{l}^{3+}}$ polarise $C{{l}^{-}}$ ions upto greater extent, therefore, $AlC{{l}_{3}}$ has covalent bond between $Al$ and $Cl-$ atoms.