Crystal Field Splitting Energy we know that an electron always prefers to occupy an orbital of a lower energy level. It is evident that if an octahedral complex contain one d electron, that electron will reside in one of the t 2g orbitals. This orbital has an energy -4 Dq compared to the energy of the hypothetical degenerate orbitals of state II as shown in fig.. Thus, the complex will be 4 will be 4 Dq more stable than predicted by the pure electrostatic theory. Evidently, the energy of the complex would now be less the decrease in energy = 0- (- 4Dq) = 4Dq is called the Crystal Field Splitting Energy (CFSE) of the complex under consideration. So the CFSE can be defined as "The energy difference of the energy of orbital in which the d-block electron exist after splitting with the energy of the degenerated d orbitals."  Calculation of  CFSE for octahedral compound As above mentioned for the filling of first electron in the  t 2g is 4Dq. So for each electron...