CIE A Level Chemistry復(fù)習(xí)筆記6.2.7 Degenerate & non-Degenerate d Orbitals

Category: A-level課程, 教材筆記, 福利干貨 Date: 2022年8月15日下午3:34

There are?five d orbitals?in an?isolated?transition element atom or ion
- An isolated transition element is one that is not bonded to anything else
These d orbitals are all at the same energy level (they are equal in energy) and are therefore said to be?degenerate orbitals
When ligands are attached, the transition element ion is?not?isolated anymore
The dative bonding from the ligands causes the five d orbitals to split into two sets
These two sets are?not?equal in energy and are described as being?non-degenerate orbitals

6.2-Chemistry-of-Transition-Elements-Degenerate-and-Non-Degenerate-Orbitals

Upon binding to ligands, the d orbitals of the transition element ion split into two non-degenerate sets of orbitals

An isolated transition element has five?degenerate?3d orbitals
Upon dative covalently bonding to a ligand, these d orbitals are split into two sets of non-degenerate orbitals

In?octahedral?complexes, there are six ligands arranged around the?central metal ion
The lone pairs of the ligands repel the electrons in the x²-y²?and z²?orbitals of the metal ion?more than?they repel the electrons in the 3d_yz, 3d_xz,?and 3d_xy?orbitals
This is because the 3d_x2-y2?and 3d_z2?orbitals line up with the dative bonds in the complex’s octahedral shape
This is because the ligands are attached to or approaching the central metal ion along the x, y and z axes, and the 3d_x2-y2?and 3d_z2?orbitals have lobes along these axes
The electrons in these two orbitals are closer to the bonding electrons, so there is more?repulsion
This means that when the d orbitals split, the 3d_x2-y2?and 3d_z2?orbitals are at a slightly higher energy level than the other three
The difference in energy between the?non-degenerate?d orbitals is labelled as?ΔE

6.2-Chemistry-of-Transition-Elements-Splitting-in-octahedral-complex

Splitting of 3d orbitals in an octahedral complex

In?tetrahedral?complexes, there are four ligands arranged around the central metal ion
The bonding pair of electrons from the four ligands now line up with the 3d_yz, 3d_xz,?and 3d_xy?orbitals of the central metal ion
Now, the 3d_x2-y2?and 3d_z2?orbitals lie between the metal-ligand bonds
Therefore, there is less repulsion with the 3d_x2-y2?and 3d_z2?orbitals
When the d orbitals split this time, the 3d_x2-y2?and 3d_z2?orbitals are at?lower?and?more?stable?energy level than the other three