Copper forms chemical compounds. In these compounds, it has two normal oxidation states: +1 and +2. +2 is more common. Most +2 copper compounds are blue. +1 copper compounds can be white. Copper compounds are weak oxidizing agents. They corrode many metals. This corrosion takes the metal and puts it in the chemical compound, leaving the copper behind. An example would be iron and copper(II) sulfate reacting to make copper and iron(II) sulfate. +1 copper compounds are reducing agents when in air. They are normally made by reduction of +2 compounds.