My chemistry tutor tells me that the general chemistry my chemical engineering department covers in two terms is covered in equal depth by my school's chemistry department. Anyway, I am new to MO theory and been trying to construct MO diagrams. It draws to me that MO theory is based on experimental results and not some qualitative theory, so unlike valence bond theory.
In constructing MO diagrams, I am not too sure how the high the antibonding orbitals and how low the bonding orbitals should be. I am not too sure how these orbitals should be placed relative to each other. eg. in drawing the MO diagram for H2, there gotta be a reason better than the fact that H2 exists, therefore the magnitude of the relative height of the antibonding orbital to the hydrogen 1s is less than that for the bonding orbital.
Moreover, in constructing a heteronulear diatomic system. eg. CO, it's pretty eveident that the 2s and 2p of oxygen is lower than that of carbon because of oxygen's higher proton number. However, given the case where I have two different energy levels to construct a single a molecular orbital, where should the pi and pi* be placed relative to it's sigma and sigma*. Perhaps someone can educate me and provide a reason why it should be so. thank you in advance.