9.5 Molecular Orbital Theory

Molecular Orbital Diagram for H2
The molecular orbital diagram for H2 indicates that is has a bond order of 1.
Bond Order = (2 - 0)/2 = 1

Molecular Orbital Diagram for He2
The molecular orbital diagram for He2 indicates that is has a bond order of 0 which means there would be no bond present in He2 indicating that it doesn't exist.
Bond Order = (2 - 2)/2 = 0

Molecular Orbital Filling Diagram for O2, F2, and Ne2
The molecular orbital filling diagram for O2 , F2, and Ne2 is different than that of the rest of the elements in the 2nd period due to a lack of sp mixing.

Molecular Orbital Diagram for O2
The molecular orbital diagram for O2 indicates that is has a bond order of 2, and the presence of unpaired electrons indicates that it is paramagnetic.
Bond Order = (8 - 4)/2 = 2

Molecular Orbital Diagram for F2
The molecular orbital diagram for F2 indicates that is has a bond order of 1, and the lack of unpaired electrons indicates that it is diamagnetic.
Bond Order = (8 - 6)/2 = 1

Molecular Orbital Diagram for Ne2
The molecular orbital diagram for Ne2 indicates that is has a bond order of 0, which means there would be no bond present in Ne2 indicating that it doesn't exist.
Bond Order = (8 - 8)/2 = 0

Molecular Orbital Filling Diagram for Li2, Be2, B2, C2,and N2
The molecular orbital filling diagram for Li2 , Be2, B2, C2, and N2 is different than that of O2, F2, and Ne2 due to sp mixing. The energy of the 2s and 2pz orbitals are much closer in energy for Li, Be, B, C, and N than for O, F, and Ne. This results in significant overlap of these orbitals that contributes to the molecular orbital picture. The ultimate result is the inversion of the σ2p and π2p molecular orbitals in the MO diagram.

Molecular Orbital Diagram for N2
The molecular orbital diagram for N2 indicates that is has a bond order of 3, and the lack of unpaired electrons indicates that it is diamagnetic.
Bond Order = (8 - 2)/2 = 3
