[ixi]

Could someone please explain to me how this works?

I know the formula is 1/2 (total bonding electrons - total antibonding electrons) but I'm not sure how to use this formula.

I found the configuration for O2 to be
 
(1 sigma g)^2 (1 sigma u *)^2 (2 sigma g)^2 (2 sigma u *)^2 (3 sigma g)^2 (1 pi u)^2 (1 pi u)^2 (1 pi g*) (1 pi g*)

How would I find the bond order for O2?

Thanks 

[tamim83]

This may help, only consider the valence electrons (i.e.-ignore the MOs made from the 1s orbitals-they are core electrons)  So there are 8 bonding electrons and 4 antibonding electrons. Now plug it into the formula and you'll have your answer. 

[ixi]

thanks