Flexi Says: Anions are negative ions that are formed when a nonmetal atom gains one or more electrons. Anions are so named because they are attracted to the anode (positive field) in an electric field. Atoms typically gain electrons so that they will have the electron configuration of a noble gas. All the elements in Group 17 have seven valence electrons due to the outer ns2np5 configuration. Therefore, each of these elements would gain one electron and become an anion with a 1− charge. Likewise, Group 16 elements form ions with a 2− charge, and the Group 15 nonmetals form ions with a 3− charge.
