Table gives some halides and oxides of the 3d series elements, selected to show the range of stable oxidation states. These follow the similar trends as required in aqueous chemistry. Compounds early in the series form compounds up to the group oxidation state, as TiO2, CrO3 and VF5. With increasing group number the bigger oxidation states become increasingly hard to form, and may be found only with oxides and/or fluorides, and sometimes only in ternary but not binary compounds. As with VV we can build VF5 and V2O5 but not VCl5.
With MnVII the only binary element is Mn2O7 but this is much less stable than ternary permanganates such as KMnO4.
The stabilization of big oxidation states by F and O can be attributed at least partly to their small size, which produces the large lattice energies necessary according to the ionic model to compensate for ionization energies.
Additional lattice stabilization is requiring in ternary structures, as in compounds such as K2CoF6 and K2FeO4 where no binary compounds with the corresponding oxidation state are stable. It would be recognized that many of the elements in greater oxidation states are not very ionic, and arguments based on the high bond strengths formed by F and O to more electropositive elements can be more satisfactory than using the ionic model.
Low oxidation states are of limited stability for the early components. The unusual metal-rich compound Sc2Cl3 has a structure with extensive Sc-Sc bonds. Compounds such VOx as and TiOx are nonstoichiometric and are also stabilized by metal-metal bonding using d electrons. With Cu the +1 oxidation state is stable and reliable in elements such as CuCl and Cu2O, but CuF is not known, presumably because the bigger lattice energy of fluorides builds this unstable with respect to disproportionation to CuF2 and Cu. The differential stability of oxidation states with distinct halogens is also shown by the existence of CuI but not CuI2.