Question

Its well-known that crystal field splitting occurs because the electrons in d orbitals repel incoming ligands and the d orbitals are no longer degenerate.

My question is now: is the repulsion (with the incoming ligands) between the electrons in the d orbitals or the orbitals itself?

Answer 1

The repulsion in crystal field splitting is between electrons in the d orbitals and incoming ligands, resulting from electrostatic interactions that cause d orbital splitting into different energy levels.

Step-by-step explanation:

The repulsion in crystal field splitting is between the electrons in the d orbitals and the incoming negatively charged ligands, not the orbitals themselves. The repulsive electrostatic interactions increase the total energy of the system and cause the d orbitals to split into two different energy levels: the higher-energy eg and lower-energy t2g orbitals. Crystal field theory treats these interactions as primarily electrostatic.

The magnitude of crystal field splitting energy (Δo for octahedral and Δ1 for tetrahedral complexes) depends on factors like the charge on the metal ion, its position in the periodic table, and the nature of the ligands.

Strong-field ligands produce large splitting and low-spin complexes, while weak-field ligands result in smaller splitting and high-spin complexes. Importantly, the total energy of the five d orbitals does not change; it remains the same before and after splitting.