1. d³ to d⁵ configuration 2. d⁵ to d⁴ configuration 3. d⁵ to d² configuration 4. d⁴ to d⁵ configuration

Answer: 4. d⁴ to d⁵ configuration Key idea: a high E^° for M³⁺/M²⁺ means M³⁺ is easily reduced to a very stable M²⁺ . mathrmMn³⁺ is d⁴ ; on reduction it becomes mathrmMn²⁺ with the stable half-filled d⁵ configuration. This extra stability makes the couple strongly positive. mathrmCr³⁺ ( d³ ) goes to d⁴ and mathrmFe³⁺ ( d⁵ ) goes to d⁶ , which give no such gain. Option 4.

Topic: Trends: ionization enthalpy, oxidation states, atomic radii· d- and f-Block Elements

The E^° value for the Mn^3+/Mn^2+ couple is more positive than that of Cr^3+/Cr^2+ or Fe^3+/Fe^2+ due to change of

1. \(d^3\) to \(d^5\) configuration

2. \(d^5\) to \(d^4\) configuration

3. \(d^5\) to \(d^2\) configuration

4. \(d^4\) to \(d^5\) configuration

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Answer: 4. \(d^4\) to \(d^5\) configuration

Key idea: a high \(E^\circ\) for \(M^{3+}/M^{2+}\) means \(M^{3+}\) is easily reduced to a very stable \(M^{2+}\).

\(\mathrm{Mn^{3+}}\) is \(d^4\); on reduction it becomes \(\mathrm{Mn^{2+}}\) with the stable half-filled \(d^5\) configuration. This extra stability makes the couple strongly positive. \(\mathrm{Cr^{3+}}\) (\(d^3\)) goes to \(d^4\) and \(\mathrm{Fe^{3+}}\) (\(d^5\)) goes to \(d^6\), which give no such gain. Option 4.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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The E^° value for the Mn^3+/Mn^2+ couple is more positive than that of Cr^3+/Cr^2+ or Fe^3+/Fe^2+ due to change of

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