The colour of the complex of d - block elements depends on the nature of the ligands whereas that of f - block elements does not. Give reason.

The colour of the complex of d - block elements depends on the nature

1.	The colour of the complex of d - block elements depends on the nature of the ligands whereas that of f - block elements does not. Give reason.
Answer» Solution :In the complexes of transition elements, the d - ORBITALS of the central metal ion splits into two sets of `t_(2g)` and `e_(g)` - orbitals in the presence of ligands. The CRYSTAL FIELD splitting, or the d - d transition of electrons is responsible for the colour of the complexes. The extent of splitting depends on the nature of the ligands. Hence, the colour of the complexes formed by the d - block elements, depends on the nature of the ligands. Similarly, the colour of the complexes formed by the f - block elements depends on the f - f transition of the electrons. Since the antipenultimate (n - 2) f - orbitals lie deep within the atom, the VALUE of crystal field splitting of the f - orbitals of the central metal ion does not depend on the nature of the ligands. Hence, the colour of the complexes formed by the d - block elements depend on the nature of ligands whereas those formed by the f - block elements does not.