# Band MO of Sodium Filling of electrons confusion

I wanted to ask a question about metallic bond - band electron theory.

Consider the diagram of Sodium below:

Circled are orbitals both containing $$2$$ electrons each which combine using LCAO to give a set of bonding and antibonding electrons.

However, the $$4$$ electrons involved in this bonding appear to only give $$3$$ electrons in the bonding and antibonding MO's produced.

This confuses me. Surely using $$4$$ electrons, I expect all $$4$$ of these electrons to also be present in the rectangle drawn.

Why are there only 3 electrons shown? Is one electron being used for the next addition of AOs?

• Ticked! By the way in your diagram for $\ce{Na3}$ the middle energy set of orbitals, is that simply missing a black dot by mistake? – vik1245 Jun 14 at 11:16