Use ionic potential phi= charge/radius as the measure of polarising power, with radii Na+=102, Ca^2+=100, Li+=76, Mg^2+=72, Al^3+=54 pm. The order of increasing covalent character of the chlorides is

NaCl < LiCl < CaCl2 < MgCl2 < AlCl3

NaCl < LiCl < MgCl2 < CaCl2 < AlCl3

LiCl < NaCl < CaCl2 < MgCl2 < AlCl3

NaCl < CaCl2 < LiCl < MgCl2 < AlCl3

NaCl < LiCl < CaCl2 < MgCl2 < AlCl3

JEE Advanced levelSingle correct optionDifficulty 3 of 3cb199

Use ionic potential $ϕ =$ charge/radius as the measure of polarising power, with radii $Na X^{+} = 102$ , $Ca X^{2 +} = 100$ , $Li X^{+} = 76$ , $Mg X^{2 +} = 72$ , $Al X^{3 +} = 54 pm$ . The order of increasing covalent character of the chlorides is

The anion is common, so rank by

ϕ

(in units of charge per pm): Na 0.0098, Li 0.0132, Ca 0.0200, Mg 0.0278, Al 0.0556. Covalent character follows

ϕ

, giving

NaCl < LiCl < CaCl X_{2} < MgCl X_{2} < AlCl X_{3}

. Note that

Ca X^{2 +}

outranks

Li X^{+}

because of its double charge.