Energy of Orbitals

It is a question arose while I was dealing with MO of sulfuric acid manually. I adopted the ligand orbital approach, that is, to interact the four oxygen 'ligand' first. I interact the four s- ligand orbitals of the four oxygen, and get four MO (don't know if the word MO is appropriate or not, as it has not yet been a molecule) that would form four sigma bonds with sulfur atom. I followed the coordinate of 'xy coordinate on this plane (so the axis out from the computer screen is the z axis)'. Then I interact the four pz orbitals to form one orbital (a), two orbitals and one orbital (a*) which is the anti-bonding orbital for (a). Besides there are 8 non-bonding orbitals (NBO) contributed only by other p orbitals of oxygens. Now, I would like to know, whether the energy of (a*) is above NBO with (a) and the other two bonding orbitals below, or it is some other ways?

A second topic I would like to discuss is about the structure of nitrate. I drew the MO diagram for NO3- for my interest, and the graph is in:

If following the diagram probably the Lewis structure drawn would be obtained. But I am curious to know if the two ligand orbitals in rectangle are correct or not. I was told that, when 3 orbitals interact, there should be a bonding, an anti-bonding, and a non-bonding orbital, actually I can't distinguish which are which amongst this three (as well as (a) to ©, I think (a) to (d) are all bonding, because each overlap maximumly with s (sigma), py (sigma), pz (sigma) and px (pi) respectively).) But I am really not sure about (e) and (f)...

Edited October 9, 200916 yr by dttom
Adding a second discussion topic