Question

Which among the following has maximum covalent character?

• A. ${\mathrm{FeCl}}_2$
• B. ${\mathrm{SnCl}}_2$
• C. ${\mathrm{AlCl}}_3$
• D. ${\mathrm{MgCl}}_2$

Answer 1

The correct option is C

${\mathrm{AlCl}}_3$

The explanation for the correct option:

C) ${\mathrm{AlCl}}_3$

• As the anion is the same we just need to check for the polarizing power of the cation, and by Fajan's rule higher the polarizing power more is the covalent nature.
• Polarizing power is directly proportional to charge density i.e. charge to radius ratio.
• ${\mathrm{Al}}^{+3}$ has the highest charge among the given and thus will be the one with the highest polarizing power.
• It has a $+3$charge, which is highest among the given compounds and thus can disturb the electron cloud more as compared to other compounds.
• Thus ${\mathrm{AlCl}}_3$ is the most covalent among the given salts.

The explanation for the incorrect options:

A) ${\mathrm{FeCl}}_2$

• Here ${\mathrm{Fe}}^{2+}$cation is present, having$+2$ charge which is less than the charge of cation present in ${\mathrm{AlCl}}_3$.
• Hence, it will have less covalent character than ${\mathrm{AlCl}}_3$.

B) ${\mathrm{SnCl}}_2$

• Here ${\mathrm{Sn}}^{2+}$cation is present, having$+2$ charge which is less than the charge of cation present in ${\mathrm{AlCl}}_3$.
• Hence, it will have less covalent character than ${\mathrm{AlCl}}_3$.

D) ${\mathrm{MgCl}}_2$

• Here ${\mathrm{Mg}}^{2+}$cation is present, having$+2$ charge which is less than the charge of cation present in ${\mathrm{AlCl}}_3$.
• Hence, it will have less covalent character than ${\mathrm{AlCl}}_3$.

Hence, option (C) is correct. ${\mathrm{AlCl}}_3$ has the maximum covalent character.