[yiyo]

I would like to ask are there any rules to construct a MO diagram for heteronuclear diatomic molecules and polyatomic molecules??? I know the basic concept to construct a MO diagram is LCAO, orbitals with similar energy and same symmetry can overlap to form a molecular orbital.

But I am confused with s-p mixing. In a MO diagram of a polyatomic molecule or heteronuclear diatomic molecule, can the atomic orbital of one atom have a s-p mixing?

I have watched a video with this link: http://www.youtube.com/watch?v=5y6F6VbnZXE
And I have some questions... Why don't we need to use s orbital of O to construct this MO diagram? Also, in my lecture note, it says s orbital of O will combined with pz orbital of O to form two sp orbitals.. It's totally different with this video.... So I don't actually know who is correct..