This neglect of orbital overlap is an especially severe approximation. In actuality, orbital overlap is a prerequisite for orbital interaction, and it is impossible to have formula_87 while formula_91. For typical bond distances (1.40 Å) as might be found in benzene, for example, the true value of the overlap for C(2p"z") orbitals on adjacent atoms "i" and "j" is about formula_92; even larger values are found when the bond distance is shorter (e.g., formula_93 ethylene). A major consequence of having nonzero overlap integrals is the fact that, compared to non-interacting isolated orbitals, bonding orbitals are not energetically stabilized by nearly as much as antibonding orbitals are destabilized. The orbital energies derived from the Hückel treatment do not account for this asymmetry ("see" Hückel solution for ethylene (below) "for details").