question_answer 28)

What is crystal field splitting energy? How does the magnitude of decide the actual configuration of d-orbital in a coordination entity?  

Answer:

When ligands approach a transition metal ion, the d-orbital split into two sets, one with lower energy and the other with higher energy. The difference of energy between the two sets of orbitals is called crystal field splitting energy (for octahedral field). The actual configuration adopted is decided by the relative value of and P (pairing energy required). If < P (pairing energy), the 4th electron enters one of the orbitals giving the configuration thus forming high spin complexes. Such ligands for which < P are called weak field ligands. If now a fifth electron is added, the configuration becomes If  the 4th electron pairs up in one of the orbitals giving the configuration  thereby forming low spin complexes. Such ligands for which  are called strong field ligands.