Which of the following has covalent bond

Options

A. `Na_(2)S`
B. `AlCl_(3)`
C. `NaH`
D. `MgCl_(2)`

Answer

d

Explanation

We know that `AI^(+3)` cation is smaller than `Na^(+)` (because of greater nuclear change) According to Fajans rule small cation polarise anion up to greater extent. Hence `AI^(3+)` polarise `CI^(-)` ion up to greater extent, therefore `AICI_(3)` has covalenrt bond between AI and CI atoms