# Oxalate ion dentiticity - why is it bidentate and not tetradentate?

Why is the oxalate ion a bidentate ligand? Why does it not act like a tetradentate ligand (having four oxygen atoms, with lone pairs)?

Perhaps you were envisioning some $\kappa^4$-bonding mode that is "side-on". However, most of the nonbonding electrons (orbitals) are also in the plane.