Passsivity promoters and dissolution moderators are identified among metallic elements and classified by considering two fundamental properties, which are the metal-oxygen bond strength and the metal-metal bond strength. Passivity promoters are elements which combine a high metal-oxygen bond strength (high heat of adsorption of oxygen or OH ( ΔH ads(ox)) with a low metal-metal bond energy ( ε M-M), because the transition from adsorbed O or OH overlayer to 3D oxide requires the breaking of metal-metal bonds. In contrast, dissolution moderators are expected to be elements with a high metal-metal bond energy. Groups of metals appear clearly in a diagram of ΔH ads (oxygen) and ε M-M.