Applying FAJAN'S RULE, smaller the cation part, larger the covalent Character. Al3+ is smallest in comparison to other cation part of other options.

Maximum covalent character in a compound

To determine the compound with the maximum covalent character among the given options, we need to analyze the nature of the bonds formed in each compound.

Covalent character in a compound

The covalent character in a compound is determined by the electronegativities of the atoms involved in the bond formation. When the electronegativities of the atoms are similar, the bond formed is covalent in nature. However, if there is a significant difference in electronegativity, the bond is more ionic in nature.

Analysis of the given compounds

a) MgCl2:
Magnesium (Mg) belongs to group 2 of the periodic table and has a lower electronegativity compared to chlorine (Cl), which belongs to group 17. The electronegativity difference between Mg and Cl is significant, indicating that the bond formed between them is more ionic than covalent.

b) FeCl2:
Iron (Fe) belongs to the transition metals and chlorine (Cl) belongs to group 17. The electronegativity difference between Fe and Cl is moderate, suggesting a partially ionic character in the bond. However, compared to MgCl2, the covalent character is expected to be higher.

c) SnCl2:
Tin (Sn) belongs to group 14, and chlorine (Cl) belongs to group 17. The electronegativity difference between Sn and Cl is relatively small, indicating a significant covalent character in the bond.

d) AlCl3:
Aluminum (Al) belongs to group 13, and chlorine (Cl) belongs to group 17. The electronegativity difference between Al and Cl is relatively small, similar to SnCl2, indicating a significant covalent character in the bond.

Conclusion

Among the given compounds, AlCl3 (option D) exhibits the maximum covalent character. This is because both aluminum and chlorine have similar electronegativities, resulting in a stronger covalent bond compared to the other compounds.