Manganese is a silvery-gray metal and is part of the group known as the transition metals. It is similar to iron. It is hard to melt, but easy to oxidize. Manganese forms chemical compounds in several oxidation states: +2, +4, and +7 are the most common. Manganese compounds can be black, brown, pink, red, green, blue, and purple. Manganese(II) compounds are pink or light brown. They are unreactive. Manganese(II) chloride is a common example. Manganese(III) compounds are weak oxidizing agents. Manganese(IV) compounds are stronger oxidizing agents, but they are rarer. They are normally black in colour. Manganese(IV) oxide is an example.