Question

What are d-d transitions?

Answer 1

1. Transition metal ions have five d-orbitals, which are normally of the same energy (degenerate).
2. When these ions combine with ligands, the d-orbitals split into two groups with different energies due to crystal field splitting.
3. d-d transitions are electronic transitions where an electron moves from a lower energy d-orbital to a higher energy d-orbital within the same metal ion.
4. These transitions occur by absorption of visible light whose energy matches the energy gap between split d-orbitals.
5. Because only specific wavelengths are absorbed, the remaining transmitted light gives the characteristic colour to the compound.
6. Ions with no unpaired d-electrons or completely full or empty d-orbitals do not show d-d transitions and are colorless.