Question

The charge/size ratio of a cation determines its polarizing power. Which one of the following sequences represents the increasing order of the polarizing order of the polarizing power of the cationic species, $K^{+},C{a}^{2+},M{g}^{2+},B{e}^{2+}$?

• A. $M{g}^{2+},B{e}^{2+},K^{+},C{a}^{2+}$
• B. $B{e}^{2+},K^{+},C{a}^{2+},M{g}^{2+}$
• C. $K^{+},C{a}^{2+},M{g}^{2+},B{e}^{2+}$
• D. $C{a}^{2+},M{g}^{2+},B{e}^{2+},K^{+}$

Answer 1

The correct option is C $K^{+},C{a}^{2+},M{g}^{2+},B{e}^{2+}$

$PolarisingPower\alpha \frac{Charge}{Radius}$

Among, ${Ca}^{+2}{,Mg}^{+2}$ and ${Be}^{+2}$, radius order is ${Ca}^{+2}>{Mg}^{+2}>{Be}^{+2}$

Polarising power order is ${Ca}^{+2}<{Mg}^{+2}<{Be}^{+2}$

Charge of $K^{+}$ is less than the remaining three and more radius than ${Be}^{+2}$.

So it has low polarising power. So, order is $K^{+}<{Ca}^{+2}<{Mg}^{+2}<{Be}^{+2}$

Hence, the correct option is C.