The charge/size ratio of a cation determines its polarizing power. Which one of the following sequences…

The charge/size ratio of a cation determines its polarizing power. Which one of the following sequences represents the increasing order of the polarizinig order of the polarizing power of the cationic species, $\mathrm{K}^{+}, \mathrm{Ca}^{2+}, \mathrm{Mg}^{2+}, \mathrm{Be}^{2+}$ ?
  1. $\mathrm{Mg}^{2+}, \mathrm{Be}^{2+}, \mathrm{K}^{+}, \mathrm{Ca}^{2+}$
  2. $\mathrm{Be}^{2+}, \mathrm{K}^{+}, \mathrm{Ca}^{2+}, \mathrm{Mg}^{2+}$
  3. $\mathrm{K}^{+}, \mathrm{Ca}^{2+}, \mathrm{Mg}^{2+}, \mathrm{Be}^{2+}$
  4. $\mathrm{Ca}^{2+}, \mathrm{Mg}^{2+}, \mathrm{Be}^{2+}, \mathrm{K}^{+}$

Solution

Higher the charge/size ratio, more is the polarizing power. $\therefore \mathrm{K}^{+} < \mathrm{Ca}^{2+} < \mathrm{Mg}^{2+} < \mathrm{Be}^{2+}$ Hence, (C) is correct.

Asked in: JEE Main 2007

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