Which of the following transition metal ions is well known to form deeply colored aqueous solutions due to d-d electronic transitions facilitated by partially filled d-orbitals?

💡 Solution & Explanation

Copper 2 plus has an outer electronic configuration of argon 3d9, possessing an incomplete d-subshell that allows d-d electron transitions when visible light is absorbed in aqueous complexes. Scandium 3 plus, titanium 4 plus, and zinc 2 plus have completely empty or fully filled d-orbitals, making their respective compounds colorless or white because d-d transitions are impossible. Ligand field theory explains how surrounding water molecules split d-orbital energy levels. Coordination number six is prevalent in many aqueous transition metal complexes.