The dot product of the gradients (slopes) of the wavefunction is important. If we compare the atomic wavefunction, \(\phi_a\), with a bonding molecular orbital, \(\psi_g = \phi_a + \phi_b\), we can see that the gradient of the wavefunction, \(\psi_g\), is smaller between the atoms than the atomic wavefunction. In comparison, the gradient of the antibonding (antiresonant state) molecular orbital, \(\psi_u = \phi_a - \phi_b\), is larger between between the atoms, which can be seen in Figure 12.
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