Question 15 Marks
What is crystal field splitting energy? How does the magnitude of $\Delta_0$ decide the actual configuration of d-orbitals in a coordination entity?
Answer
View full question & answer→The degenerate d-orbitals (in a spherical field environment) split into two levels i.e., $e_g a n d, t_{2 g}$ in the presence of ligands. The splitting of the degenerate levels due to the presence of ligands is called the crystal-field splitting while the energy difference between the two levels ( $e_g$ and $t_{2 g}$ ) is called the crystal-field splitting energy. It is denoted by $\Delta_0$ After the orbitals have split, the filling of the electrons takes place. After 1 electron (each) has been filled in the three $t_{2 g}$ orbitals, the filling of the fourth electron takes place in two ways. It can enter the $e_g$ orbital (giving rise to $t_{2 g}^3 e_g^1$ like electronic configuration) or the pairing of the electrons can take place in the $t_{2 g}$ orbitals (giving rise to $t_{2 g}^4 e_g^0$ like electronic configuration). If the $\Delta_0$ value of a ligand is less than the pairing energy $( P )$, then the electrons enter the $e_g$ orbital. On the other hand, if the $\Delta_0$ value of a ligand is more than the pairing energy (P), then the electrons enter the $t_{2 g}$ orbital.
