Question

The colour of the transition metal ions is due to

• A. $\text{d-d}$ transition
• B. Change in geometry
• C. Variable oxidation states
• D. None of these

Answer 1

Answer: (A)

The colour of transition metal ions is due to $\text{d-d}$ transition. When a ligand approaches metal ion, its $\text{d}$ -orbital does not remains degenerate.

They split into two sets, one consisting of lower energy and the other consisting higher energy level.

Thus electrons can jump from lower energy $\text{d}$ -orbitals to higher energy $\text{d}$ -orbitals. Such transition are known as $\text{d-d}$ transition.

The required amount of energy during $\text{d-d}$ transition is obtained by absorption of light of a particular wavelength in the region of visible light.

Note: Sometimes the colour of transition metal ions is also due to charge transfer spectra.