Identify the factor responsible for colour of transition metal compounds.

Step-by-step solution

The colour of transition metal compounds is primarily due to d-d transitions. In transition metal complexes, the five degenerate d-orbitals split into two sets of different energies (e.g., t_ 2g and e_g in an octahedral field) due to the presence of ligands. When white light falls on the complex, an electron from a lower energy d-orbital absorbs a specific wavelength of light and gets excited to a higher energy d-orbital. The transmitted or reflected light, which is complementary to the absorbed colour, is responsi