Question

13. Construct energy-level diagrams for both high- and low-spin situations for the d6 electron configuration in (a) an octahedral field; (b) a tetrahedral field.

Please explain if possible...I do understand the orbital principle generally. Thank you.

Answer 1

in octa hedral complex , ligands approach the central ion through coordinate axes. . so electrons present in orbitals which are present on the co ordinate axes will experience more repulsion from the ligands.

so among five d-orbitals two orbitals designated by d_x²-y²  and d_z² orbitals present along the axes, they are called as e_g orbitals.

another three orbitals d_xy ,d_yz and d_xz  are present in between the axes. they are called as t_2g orbitals.

so in octa hedral complex e_g orbitals feel more repulsion than t_2g orbitals .so energy of e_g orbitals is higher than t_2g orbitals.

in presence of strong field ligand the energy gap between e_g and t_2g orbitals is high. as a result the electrons first enters in lower energy t_2gorbitals. after filling of these orbitals the remailing electrons will go to e_g orbitals. here electron distribution takes place against Hund's rule . here pairing of electrons takes place. unpaired electrons are not present . so they are low spin complexes.

in presence of strong field ligand the energy gap between e_g and t_2g orbitals is low. as a result the electrons first enters in lower energy t_2gorbitals. after half filling of these orbitals the remailing electrons will go to e_g orbitals. here electron distribution follows Hund's rule . here pairing of electrons takes place if needed. so unpaired electrons are present . so they are high spin complexes.

in tetrahedral complexes, ligands approach central meetal ion in between the axes. so in this case d- orbitals which are present along axes feel more repulsion than the d-orbitals which are along the axes. that is t_2g orbitals have more energy than e_g orbitals

in presence of strong field ligand the energy gap between t_2g and e_g orbitals is high. as a result the electrons first enters in lower energy e_gorbitals. after filling of these orbitals the remailing electrons will go to t_2g orbitals. here electron distribution takes place against Hund's rule . here pairing of electrons takes place. unpaired electrons are not present . so they are low spin complexes.

in presence of strong field ligand the energy gap between t_2g and e_g orbitals is high. as a result the electrons first enters in lower energy e_gorbitals. after half filling of these orbitals the remailing electrons will go to t_2g orbitals. here electron distribution follows Hund's rule . here . unpaired electrons are present . so they are high spin complexes.