Question

The electronic configuration of Cu(II) is 3d⁹ whereas that of Cu(I) is 3d¹⁰. Which of the following is correct ?

• A. Cu(II) is less stable
• B. Stability of Cu(I) and Cu(II) depends on nature of copper salts
• C. Cu(II) is more stable
• D. Cu(I) and Cu(II) are equally stable

Answer 1

The Correct Option is C

The question asks about the stability of copper in its different oxidation states, Cu(I) and Cu(II). To determine which is more stable under standard conditions, we need to consider both the electronic configuration and some known empirical facts about copper salts.

Electronic Configuration:

• The electronic configuration of Cu(II) is 3d⁹.
• The electronic configuration of Cu(I) is 3d¹⁰.

Cu(II) has one less electron in the d-orbital compared to Cu(I). In terms of electronic configuration, a completely filled or half-filled d-orbital is generally more stable. Yet, in this case, the d⁹ configuration of Cu(II) may initially appear less stable compared to the d¹⁰ of Cu(I).

Stability of Copper Oxidation States:

The stability of different oxidation states of an element can be influenced by various factors, including lattice energy, solvation energy, and the Jahn-Teller effect:

• Jahn-Teller Effect: Cu(II)'s d⁹ configuration is subject to Jahn-Teller distortion, leading to stabilization.
• Coordination Chemistry: Cu(II) is more stable in aqueous solution due to the higher hydration energy compared to Cu(I).

Considering the above factors, Cu(II) is generally more stable than Cu(I) in aqueous solution, and the empirical evidence from copper salts often shows that Cu(II) compounds are more common and stable.

Conclusion:

The correct answer is: Cu(II) is more stable. Therefore, the assertion that "Cu(II) is more stable" is supported by the greater stability of Cu(II) due to factors like the Jahn-Teller effect and higher hydration energy.

Answer 2

• The stability of Cu(II) arises because it has a partially filled d-subshell (\(3d^9\)), which allows it to participate in ligand bonding and form complexes more effectively.
• Cu(I) with \(3d^{10}\) is more stable in certain cases due to the completely filled d-subshell, but Cu(II) is generally more stable in aqueous solutions.
• The higher stability of Cu(II) over Cu(I) in aqueous medium is attributed to the higher hydration enthalpy of Cu(II) ions.