Question

The increasing order of covalent character of \(\mathrm{NaCl}\) (I), \(\mathrm{RbCl}\) (II), \(\mathrm{MgCl}_2\) (III), \(\mathrm{AlCl}_3\) (IV) is:

• A. \(I, II, III, IV\)
• B. \(IV, II, I, III\)
• C. \(II, I, III, IV\)
• D. \(III, I, II, IV\)

Hint:

Higher charge and smaller size of cations increase covalent character by greater polarization of anion.

Answer 1

The Correct Option is C

Covalent character depends on polarization ability of cation and polarizability of anion. 
- \(Rb^+\) is larger than \(Na^+\), so less polarization → less covalent (II) 
- \(Na^+\) smaller than \(Rb^+\), more polarization → more covalent (I) 
- \(Mg^{2+}\) with higher charge density → more covalent (III) 
- \(Al^{3+}\) with even higher charge density → most covalent (IV) 
So order of increasing covalent character: \[ RbCl<NaCl<MgCl_2<AlCl_3 \]