Among the following transition metal compounds, which one is expected to be coloured in its solid state or aqueous solution?

Step-by-step solution

The colour of transition metal ions is generally due to d-d transitions, which require the presence of unpaired d-electrons. In TiCl ₄ , the oxidation state of titanium is +4 . The electronic configuration of Ti ⁴⁺ is [ Ar ] 3d^0 . Since it has no d-electrons, it cannot undergo d-d transitions and is colourless. In Cu ₂ Cl ₂ , the oxidation state of copper is +1 . The electronic configuration of Cu ⁺ is [ Ar ] 3d¹⁰ . Since the d-subshell is completely filled, there are no unpaired electrons, making it colourless. I