Fig. 8-4. Molecular orbital energy level
diagram for homonuclear diatomic molecules showing the correlation of the
molecular orbitals with the atomic orbitals of the separated atoms. The
schematic representation of the molecular orbitals is to illustrate their
general forms and nodal properties (the nodes are indicated by dashed lines).
Only one component of the degenerate 1pu
and 1pg orbitals is shown.
The second component is identical in form in each case but rotated 90°
out of the plane. The ordering of the orbital energy levels shown in the
figure holds generally for all homonuclear diatomic molecules with the
exception of the levels for the 1pu
and 3sg orbitals, whose relative
order is reversed for the molecules after C2.