CBSE Class 12-science Answered

Under the experience of negative fied due to ligands or neutral molecules which have lone pair of electrons,the d-orbitals split into two levels i.e.t_2g and e_g.

When the complex is formed, the ligands destroy the degeneracy(same energy level) of these orbitals i.e.the orbitals have now different energies.In an isolated gaseous metal ion the five d-orbitals do all have same energy termed as degenerate.However,the energy of orbitals is raised because of repulsion between the field and the electrons on the metal.In most transition metal complexes either six or four ligands surround to metal giving octahedral or tetrahedral structures.

    In these two cases the field produced by the ligand is not spherically symmetrcal.Thus,the d-orbitals are not all affected equally by ligand field and thus become asymmetrical.