(a) Which of the following species has greater polarising power ?
`(i) Fe^(3+)or Fe^(2+) (ii) Cu^(2+) or Na^(+) (iii) Mg^(2+) or Al^(3+).`
(b) Which of the following species is most susceptible to polarisation ?
`(i) Br^(-)orI^(-)(ii)O^(2-)or S^(2-)(iii) N^(3-)orO^(2-)`

Explanation

To solve the question step by step, we will analyze each part separately.

### Part (a): Which of the following species has greater polarizing power?

1. **Comparison of Fe³⁺ and Fe²⁺:**
- **Size:** Both ions are derived from the same element (iron), so their sizes are similar.
- **Charge:** Fe³⁺ has a charge of +3, while Fe²⁺ has a charge of +2.
- **Conclusion:** According to Fajans' rule, a smaller cation with a higher charge has greater polarizing power. Therefore, **Fe³⁺ has greater polarizing power than Fe²⁺.**
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