Transition metals share some typical properties that Group 1 and Group 2 metals do not. First, many transition elements form ions with different charges. Iron forms Fe2+ and Fe3+ ions, copper forms Cu+ and Cu2+, and manganese and chromium can also form ions with more than one charge. A Group 1 metal always forms the same ion, for example Na+. The Roman numeral in a name shows the charge, so iron(III) chloride contains Fe3+ ions.
Second, transition metal compounds are often coloured. Copper(II) sulfate solution is blue, iron(II) compounds are usually green, iron(III) compounds are orange-brown, and nickel(II) compounds are green. Potassium manganate(VII) is purple, and chromium compounds can be green, yellow or orange. Compounds of Group 1 metals are normally white, or colourless in solution.
Third, transition metals and their compounds are useful as catalysts. A catalyst speeds up a reaction without being used up. Iron is the catalyst in the Haber process for making ammonia, nickel is used as a catalyst when alkenes react with hydrogen, and manganese(IV) oxide speeds up the breakdown of hydrogen peroxide into water and oxygen.