Because they contain one or more empty orbitals, metal ions such as Li+ and Mg2+ can accept pairs of electrons from a donating species. By accepting electron pairs from ligands, these ions tend to form coordination compounds. The majority of metal ions have a coordinated structure with some ligands. To donate an electron pair to a Lewis base, the metal ion must first dissociate from the ligand. These ions' Lewis adducts are typically complexes as well.