Molecular orbital model antibonding

The molecular orbital model can also be applied to complexes of the d-block elements. In octahedral complexes the d-orbitals of the metal are not degenerate, as they are in the free metal, because of the interaction between the ligand and metal orbitals. The five d-orbitals are split into three t2g (nonbonding) and two e (antibonding) MOs that is ... 

In the molecular orbital model, the number of bonds between two atoms is designated as the bond order and depends not only on the number of bonding electrons, but also on the number of antibonding electrons. In general, the bond order can be determined from the following equation.4... 

Structure of 1,3-butadiene— molecular orbital model. Combination of four parallel Ip atomic orbitals gives two TT-bonding MOs and two TT-antibonding MOs. 

Butadiene has two n bonds. The interaction between the two n bonds is one of the simplest models to derive molecular orbitals from bond orbitals. A n bond in butadiene is similar to that in ethylene. The n bond is represented by the bonding and antibonding orbitals. The interactions occur between the n bonds in butadiene. The bond interactions are represented by the bond orbital interactions. 

---