Question

The red color of ruby is due to __________

Answer 1

d-d transition

It is shifting electrons from lower energy d orbital to d orbital with higher energy by absorbing the energy and vice versa.

For complex compounds, the electronic transition occurs from t_2g orbital to E_g orbital.

Ruby

1. It is a gemstone with a pink to red color. It is the mineral corundum i.e.Aluminium oxide.

2. The mineral corundum is a crystalline form of alumina: Al₂O₃. A pure crystal of alumina is colorless.

3. However, if just 1% of the Al³⁺ ions are replaced with Cr³⁺ ions, the mineral becomes deep red in color.

Hence the red color of Ruby is due to the d-d transition of Cr³⁺ ion in the Al₂O₃ lattice.