The charge/size ratio of a cation determines its polarizing power. Which one of the following sequences represents the increasing order of the polarizing power of the cationic species, `K^(+), Ca^(2+), Mg^(2+), Ba^(2+)`?

Options

A. `Be^(2+) ltK^(+) ltCa^(2+) ltMg^(2+)`
B. `K^(+)ltCa^(2+)ltMg^(2+)ltBe^(2+)`
C. `Mg^(2+)ltBe^(2+)ltK^(+)ltCa^(2+)`
D. `Ca^(2+)ltMg^(2+)ltBe^(2+)ltK^(+)`

Answer

B

Explanation

Polarizing power of cation increases with increase of charge and decrease of size as this leads to higher charge density (charge/size). Dipositive alkaline earth metal ions are more polarizing than univalent alkali metal ions. Size of dipositive alkaline earth metal ions increases as we move down the group. Thus, increase in the order of charge density and, hence, polarizing power is `K^(+)ltCa^(2+)ltMg^(2+)ltBe^(2+)`.