Question

Compounds of ‘d’ block elements are coloured in solid state as well as in an aqueous state. Explain.

Answer 1

1. The transition elements contain unpaired electrons in the d orbitals of their atoms.
2. When the atoms are free or isolated, the five d orbitals are degenerate (have the same energy).
3. In complexes, ligands or solvent molecules surround the metal ions. These have an impact on the energy of d orbitals, causing their energies to change. There are two groups of d orbitals: a higher energy group and a lower energy group.
4. The atom absorbs a portion of the energy as white light travels through it, while the remaining light is transmitted. As a result, the electron in the lower energy group orbital gets promoted to one of the higher energy group’s d orbitals.
5. This d-d transition is responsible for the colour of d-block (transition) elements.
6. The colour of the element is complementary to the transmitted light.