doubt in the answer

Question

The E° value for the Mn³⁺/Mn²⁺ couple is more positive than that of Cr³⁺/Cr²⁺ or Fe³⁺/Fe²⁺ due to change of

(1) d⁴ to d⁵ configuration

(2) d³ to d⁵ configuration

(3) d⁵ to d⁴ configuration

(4) d⁵ to d² configuration

Answer 1

Correct option is (1) d⁴ to d⁵ configuration

1. Mn³⁺ has a d⁴ configuration, which upon reduction to Mn²⁺ becomes d⁵, a half-filled stable configuration.

2. This stability contributes to the more positive \(E^\circ\) value for Mn³⁺/Mn²⁺ compared to Cr or Fe.