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Assertion: Cu²+(aq) is more stable than Cu^+(aq) in aqueous solution. Reason: Electrode potential plays a more decisive role in determining the stable oxidation state of a metal in solution than its electronic configuration does.

1. Both Assertion and Reason are true; Reason is the correct explanation of Assertion.
2. Both Assertion and Reason are true; Reason is NOT a correct explanation of Assertion.
3. Assertion is true; Reason is false.
4. Assertion is false; Reason is true.

Correct answer: Both Assertion and Reason are true; Reason is the correct explanation of Assertion.

Solution

Although Cu⁺ (3d¹⁰) has a stable closed-shell configuration, Cu²+ is thermodynamically preferred in aqueous solution because its high charge density leads to a very large hydration enthalpy. This makes the disproportionation 2Cu^+(aq) -> Cu(s) + Cu²+(aq) spontaneous. Electrode potential (which encodes all thermodynamic factors including hydration) is therefore the correct criterion for stability in solution, not merely electronic configuration.

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