Unlike most elements, phosphorus can take a wide range of oxidation states from -3 to +5 in solid-state materials. PSs are an ideal material family to see these extreme oxidation states in action. We have already seen that compounds with P/S ≤ 1/3 prefer high positive oxidation states for phosphorus (+5, +4), whereas negative oxidation states (-1,-2,-3) are favored in compounds with P/S ≥ 1. Since phosphorus can easily form bonds with other P atoms in the solid state, all other intermediate oxidation states are in principle possible. The availability of such a wide range of oxidation states indicates that there should be many combinations of elemental compositions that satisfy the requirement of charge neutrality. This translates into a large number of hypothetical PS materials that are chemically plausible and not intrinsically metallic.