Molecular Orbital theory question

pigeonwarrior

What is the bond order of PF3 with a charge of 2+? The answer is 0.5.
Some help would be great!

Reply 1

TypicalNerd

Original post by Nitrotoluene

Open the spoiler, pigeonwarrior!😀

**Molecular Orbital Theory Question**

There is no way this is a correct approach. For starters, how on earth does 2 = 0.5?

I have doubts about the numbers of bonding and antibonding electrons you have said there are. I think should be 24 valence electrons (3 in P^2+ and 7 in each F), but if there are 10 bonding electrons and 6 antibonding electrons, that leaves just 8 non-bonding electrons. These numbers of electrons would also suggest that the bond order would be 2 and not 0.5, which is apparently not the answer.

Also, bond order is in MO theory is just defined as (bonding electrons - antibonding electrons)/2 and is not calculated as such because the ion has lost two electrons.

Unfortunately, I cannot offer an alternative explanation as to where 0.5 came from as I am not familiar enough with MO theory, the relevant orbital energies and molecular symmetry to construct an MO diagram for PF3^2+. I would guess it belongs to the D3h point group, if that is remotely helpful for anyone better versed in MO theory to construct the relevant diagram.