When degenerate d-orbitals of an isolated atom/ion come under influence of magnetic field of ligands, the degeneray is lost. The two set t_(2g)(d_(xy),d_(yz),d_(xz)) and e_(g) (d_(x^(2))-d_(x^(2)-y^(2)) are either stabilized or destabilized depending upon the nature of magnetic field. it can be expressed diagrammatically as: Value of CFSE depends upon nature of ligand and a spectrochemical series has been made experimentally, for tetrahedral complexes, Delta is about 4/9 times to Delta_(0) (CFSE for octahedral complex). this energy lies in visible region and i.e., why electronic transition are responsible for colour. such transition are not possible with d^(0) and d^(10) configuration. Q. Cr^(3+) form four complexes with four different ligands which are [Cr(Cl)_(6)]^(3-), [Cr(H_(2)O)_(6)]^(3+), [Cr(NH_(3))_(6)]^(3+) and [Cr(CN)_(6)]^(3-), the order of CFSE (Delta_(0)) in these complexes in the order: