Octahedral and tetrahedral complexes made of the same metal ion have different coloures. Explain.

Explanation

The relation between the crystal field splitting energy of an octahedral `(Delta_(0))` and a tetrahedral complex `(Delta_(t))` made of the same metal ion and the same ligand, can be given by `Delta_(t)=(4)/(9)Delta_(0) or Delta_(t) lt Delta_(0)`
Hence, transfer of electron from `t_(2g)` to `e_(g)` orbitals (in case of octahedral complexes) or from `e` to `t_(2)` orbitals (in case of tetrahedral complexes) requires different amount of energy and so different wavelengths of light from visible spectrum is absorbed. Therefore, given complexes have different colours.