How do you write the orbital diagram for phosphate?
I interpreted this as the molecular orbital diagram... and it became rather complicated (I honestly don't think you want to know the minor details!).
Here's the scratchwork when I was getting the reducible representations
The whole point of that was to see how the oxygen orbital energies split up (and which were two-fold or three-fold degenerate). It was also to figure out which orbitals on phosphorus interact with which orbitals on the oxygen atoms.
The resultant MO diagram was:
- This is only qualitative, so take it with a grain of salt.
- Phosphate has all electrons paired.
- The nonbonding orbitals are nonbonding either due to mismatched symmetries, overly different inner-atom/outer-atom orbital energies, or interactions between both high-lying and low-lying orbitals.
- There are
#22#nonbonding electrons, which accounts for all #11#lone pairs of electrons that belong to the oxygen atoms. The remaining #2#nonbonding electrons account for the #bb(pi)#bond that is delocalized.
#sigma#bond order that this MO diagram seems to account for is #1#for all four #bb(sigma)#bonds, as there are four clearly-bonding MOs ( #a_1 + t_2#), one for each bond.