Arrange the following in the decreasing order of covalent character: (A) LiCl (B) NaCl (C) KCl (D) CsCl

🧠 Covalent character increases with smaller cation size (Fajan's rules: higher charge density → more polarisation of anion → more covalent). All four are alkali metal chlorides with M⁺ charge.

Ionic radii: $\ce{Li+}$(76 pm) < $\ce{Na+}$(102 pm) < $\ce{K+}$(138 pm) < $\ce{Cs+}$(167 pm)

Smaller $r$ → greater charge density → greater polarising power → more covalent character.

$\ce{LiCl > NaCl > KCl > CsCl}$ in decreasing covalent character.

⚠️ Trap: Option (d) has D (CsCl) before C (KCl), but $\ce{Cs+}$ is largest → least polarising → least covalent → it should come last.

$\boxed{\text{Answer: (c) A > B > C > D (LiCl > NaCl > KCl > CsCl)}}$