Question

Discuss the following property with respect to transition elements:

Colour of ions.

Answer 1

1. Transition metal ions have unpaired electrons in their d-orbitals.
2. These electrons can absorb visible light and get excited from lower to higher energy d-orbitals (d-d transition).
3. The absorbed light corresponds to a specific wavelength, and the transmitted light shows the complementary colour.
4. Ions with completely filled or empty d-orbitals are colourless as d-d transitions do not occur.
5. Example: Cu²⁺ appears blue because it absorbs red light, and Co²⁺ appears pink due to absorption of blue-green light.
6. Colours depend on the type of ion, number of unpaired electrons, and nature of ligands around the metal ion.