Chemistry - Complete d-block Question with Solution | TestHub

The correct answer is (D) Cr³⁺.

Transition metal ions absorb light in the visible region primarily due to the excitation of electrons in d-d transitions.

These transitions are only possible when the metal ion possesses a partially filled d-subshell ($d^1$ to $d^9$).

The ions Sc³⁺ ($3d^0$), Cu⁺ ($3d^{10}$), and Cd²⁺ ($4d^{10}$) have empty or completely filled d-orbitals, so they cannot undergo d-d transitions.

Only Cr³⁺ has a partially filled configuration ($3d^3$), which allows it to absorb light in the visible spectrum and appear colored.