Among the following the maximum covalent character is shown by the compound:

Correct option is A

The correct answer is (a) AlCl3

Explanation:
• According to Fajan's Rules, covalent character increases with increasing charge on the cation and decreasing size of the cation.
• Here, Al³⁺ has the highest charge (+3) compared to Mg²⁺, Sn²⁺, and Fe²⁺ (+2).
• The higher charge-to-size ratio leads to greater polarization of the chloride ion, resulting in maximum covalent character.

Information Booster:
• $AlCl_3$ is so covalent that it exists as a dimer (Al₂Cl₆) in the vapor state.
• Polarizing power $\propto$ Charge / Size.

Additional Knowledge:
MgCl2 (Option b)
• More ionic than $AlCl_3$ due to lower charge (+2) and larger size of Mg²⁺.
SnCl2 (Option c)
• A post-transition metal chloride; less covalent than $AlCl_3$.
FeCl2 (Option d)
• Transition metal chloride; has covalent character but Al³⁺ dominates due to higher charge density.

So the correct answer is (a)