The first two methods are prone to failure for more exotic structures, and the fallback method, maxiumum electronegativity, is very simplistic and can yield incorrect predictions. For example, the most electronegative element in any chlorate salt is chlorine, but chlorine is not in a negative oxidation state. Additionally, for any structure that is mostly a non-metal with a very small amount of metal, this method would assume that all of the nonmetal atoms are negatively charged, when in fact only some of them are.