[sd79812]

>-Atomic orbitals must be at the similar energy levels to combine as molecular orbitals, said Wikipedia.


This is unclear. How do you quantify how "similar" means?

I heard electronegative is tied to atomic radius is tied to atomic orbital energy.


What are two atoms that would in theory form an ionic compound if you use a naive theory but actually don't because the atomic orbitals are too dissimilar in energy levels according to molecular orbital theory?

>The essential point of Pauling electronegativity is that there is an underlying, quite accurate, semi-empirical formula for dissociation energies, namely:
>$$
E_{\mathrm{d}}(\mathrm{AB})=\frac{E_{\mathrm{d}}(\mathrm{AA})+E_{\mathrm{d}}(\mathrm{BB})}{2}+\left(\chi_{\mathrm{A}}-\chi_{\mathrm{B}}\right)^2 \mathrm{eV}
$$

According to this equation, you have a stronger bond when the atomic orbital energy difference  $$(\chi_A-\chi_B)$$ is high. Does this equation contradict the first quote?