So I'm taking an introductory chemical physics course and we are covering LCAO-MO. We learn about the molecular orbitals that arise out of a combination of the two atoms atomic orbitals. This totally makes sense to me, but then we start learning about electron configurations and orbital diagrams. When we get to oxygen the textbook shows that oxygen has 8 electrons each, and when they combine they fill up the σ1s σ2s σ2pz π2px π2py bonding orbitals and the σ*1s σ*2s antibonding orbitals (with the π*2px π*2py antibonding orbitals each half filled). My question is:
Why does this result as a double bond?
I see it is partially addressed here: Molecular Orbital Theory and No. of bonds
But what they don't speak to is why there are two filled π2p bonding orbitals but only one pi bond. I understand how to calculate bond order but in my understanding thats our approach at reasoning out bond strength, it returns an integer value - it does not really tell me much about the actual bonds themselves. Is the pi bond that results some sort of hybrid between the π2px and π2py orbital? If there are two electrons each in the π2px and π2py orbitals, how does one electron in each of their respective antibonding orbitals play out in the formation of the bond?
Thank you ChemSE community!
*editted to further clarify I am aware of bond order calculations