Show pz orbitals or Orbitals off
Show the highest energy MO, E=-0.246 eV
Show the second highest-energy MO, E=-0.246 eV
Show the lower energy MO, =-.359eV

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Spacefilling model
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Ball & Stick

 The buttons are listed in descending order of energy.
These represent different ways the p atomic orbitals mix to form MOs. Another representation is below:
Occupied MOs of benzene. Lowest MO is all-in-phase p orbitals, E=-0.359 eV. There are two HOMOs at -0.246 eV, each with one node. The first has the node along the C1-C4 axis, with no contribution from those two atoms. The second has the node between atoms 2 and 3, and between atoms 5 and 6 (perpendicular to the first).

Compare this to the resonance picture, which correctly describes all carbons as being identical,and makes all the C-C bonds identical, but misses that there are two HOMOs of identical energy but one more stable filled MO to account for the six electrons.
Two resonance forms of benzene: difference is only in the formal location of double bonds. The real structure is a hybrid of the two.

(I have not shown any of the empty, antibonding MOs. See Fig. 15-4 in Vollhardt & Schore.)
While we are not covering the underlying principles of how we arrive at the molecular orbitals, you can get more background at these links:
The Wikipedia page on a simplified method for calculating π MOs
A Simple Huckel MO calculator (requires an active Java plugin)
A Javascript-based SHMO calculator that requires an understanding of the mathematecal approach outlineed in the Wikipedia page


Last updated: 12/15/2019