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Could someone please show me the MO diagram for $\ce{N_2^{2-}}$? What I did was since N has 5 valence $\ce{e^{-}}$, then $\ce{N_2}$ must have 10, and $\ce{N_2^{2-}}$ must have 12. And $\ce{N}$ has $s$ and $p$ orbital mixing. So when I draw out the MO it has all the orbitals filled. And the bond order is $\frac{1}{2}(6-6)=0$, but this is apparently wrong. Because according to the lewis structure the bond order should be $2$ I think.

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N2 MOhttp://h2g2.com/edited_entry/A1011899

This an image of the molecular orbital of $\ce{N2}$. If we add 2 more electrons, they will enter singly into the 2 antibonding pi orbitals and since bond strength is defined as bonding electrons minus nonbonding electrons over 2, or as I prefer, the net number of bonding/ nonbonding electrons times half, we would subtract 1 from the original bond order of $\ce{N2}$ to get 2.

Here is the mathematical calculations:

$\frac{1}{2}(8 (bonding)-4(antibonding))=2$

Antibonding orbitals are shown by an asterisk. Note that you will need draw in the 2 electrons on your own.

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