ions (M31). Thus for Groups 1 through 3 the charges of the cations formed are identical to the group numbers.In contrast to the Group 1, 2, and 3 metals, most of the many transition metals form cations with various positive charges. For these elements there is no easy way to predict the charge of the cation that will be formed.Note that metals always form positive ions. This tendency to lose electrons is a fundamental characteristic of metals. Nonmetals, on the other hand, form negative ions by gaining electrons. Note that the Group 7 atoms all gain one electron to form 12 ions and that all the nonmetals in Group 6 gain two electrons to form 22 ions.At this point you should memorize the relationships between the group number and the type of ion formed, as shown in Fig. 4.17. You will understand why these relationships exist after we further discuss the theory of the atom in Chapter 11.