The energy-level diagram for these six MO's appears at the right. As we have seen consistently in other AO's and MO's, the general principle holds that, other things being equal, the more nodes of zero probability in an orbital, the higher its energy. Six p atomic orbitals are combined to form six molecular orbitals-three bonding and three antibonding. The six electrons not used in the o, framework of the benzene molecule are used to fill the three bonding MO's, and the antibonding orbitals are unused. The benzene ring therefore has three more bonds in addition to its s-bonded skeleton, but these three bonds are spread around the entire ring rather than being localized between pairs of carbon atoms, as the Kekule or Dewar models would predict. All of the carbon-carbon bonds in the ring are intermediate between "single" and "double," and their observed bond length verifies this.