The electron-gaining property of an oxidizing agent is called its oxidizing power, which is determined by the electron-gaining tendency of the higher-valence elements in the substance. In solution, according to the double-layer theory, the magnitude of oxidizing power is reflected in the standard hydrogen electrode potential of the oxidizing agent: the higher the potential, the stronger the oxidizing power; the lower the potential, the weaker the oxidizing power, and correspondingly, the stronger the reducing power of its reduced state. In water, the oxidation reaction of most oxidizing agents involves three steps: dissociation, affinity, and combination. These three steps determine the enthalpy of the half-reaction of the oxidation reaction, which has a significant impact on the oxidizing power of the oxidizing agent.
Hydrogen ions also play a significant role in the oxidizing power of oxygen-containing oxidizing agents because hydrogen ions have a very strong anti-polarization ability, making the X-O bond (X refers to the central atom of the oxidizing agent) unstable. Therefore, generally, the oxidizing power of oxidizing agents is stronger under acidic conditions than under alkaline conditions. For some species unaffected by hydrogen ions, such as Cl2 and Br2, their oxidizing power is independent of pH.
