The phrase "oxidation state" refers to the level of charge or electron distribution of an atom within a compound. It helps determine which atoms are gaining or losing electrons during a chemical reaction. Full definition
He then outlines the various oxidation states of iron — the origin of its wealthy chemistry. (newscientist.com)
Simply having different oxidation states is not enough to make an element work for a liquid battery. (discovermagazine.com)
They focused on the satellite structures and showed that the energy separation between the satellite and primary peaks was diagnostic of uranium oxidation states over a broad range of compounds with very different compositions. (pnnl.gov)