When degenerate d-orbitals of an isolated atom/ion come under influence of magnetic field of ligands, the degeneracy is lost. The two sets t_(2g)(d_(xy),d_(yz),d_(xz))ande_(g)(d_(z^(2)),d_(x^(2)-y^(3))) are either stabilized or destabilized depending upon the nature of magnetic field. It can be expressed diagramatically as : Value of CFS depends upon nature of ligand and a spectro-chemical series has been made experiment-ally, for tetrahedral complexes Delta_(i) is about 4/9 times to Delta_(0) (CFSE for octahedral complexes). The energy lies in visible region and i.e., why electronic transition t_(2_(g))hArre_(g) are responsible for colour. Such transitions are not possible with d^(0) and d^(10) configuration. The value of CFSE (Delta_(a)) for complexes given below follow the order:{:([Co(NH_(3))_(6)]^(3+),[Rh(NH_(3))_(6)]^(3+),[Ir(NH_(3))_(6)]^(3+)),("(I)","(II)","(III)"):}