Question

Identify the correct order of polarizing power of given cations: 
 

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

Hint:

When comparing the polarizing power of cations, consider both their ionic radii and their charges; smaller and more highly charged cations generally have higher polarizing power.

Answer 1

The Correct Option is B

Polarizing power of a cation is influenced by its charge density, which in turn depends on both the charge and the size of the ion. Higher charge and smaller size lead to a higher charge density, thus greater polarizing power. Among the given cations:
- \({K}^+\) is a larger cation with a +1 charge, having the least polarizing power.
- \({Ca}^{2+}\) is smaller than \({K}^+\) and has a +2 charge.
- \({Mg}^{2+}\) is smaller than \({Ca}^{2+}\) with a similar +2 charge, increasing its polarizing power.
- \({Be}^{2+}\) is the smallest among them and also has a +2 charge, making it have the highest polarizing power.