Question

The charge/size ratio of a carbon determines its polarising power. Which one of the following sequences represents the increasing order of the polarising power of the cationic species,
$K^{+},{Ca}^{2+},{Mg}^{2+},{Be}^{2+}$?

• A. ${Mg}^{2+}<{Be}^{2+}<K^{+}<{Ca}^{2+}$
• B. ${Be}^{2+}<K^{+}<{Ca}^{2+}<{Mg}^{2+}$
• C. $K^{+}<{Ca}^{2+}<{Mg}^{2+}<{Be}^{2+}$
• D. ${Ca}^{2+}<{Mg}^{2+}<{Be}^{2+}<K^{+}$

Answer 1

The correct option is C $K^{+}<{Ca}^{2+}<{Mg}^{2+}<{Be}^{2+}$

Answer is option $C.$

High charge and small size of cations increases the polarisation.

Size of given cations decreases as, $K^{+}>C{a}^{2+}>M{g}^{2+}>B{e}^{2+}$

Hence, polarising power decreases as, $K^{+}<C{a}^{2+}<M{g}^{2+}<B{e}^{2+}$