Suppose now we have a neutral atom with a plus one charge and a minus one charge, forming a neutral charge. And now suppose it gains an electron from some other atom, probably metal. Now what will happen is it will gain a new outer shell, forming this outer shell and forming this empty space in between. And that means anions. When they gain electrons, this causes our atom or element, to grow in size. So cations, or the formation of cations, decrease the size of our atom, while the formation of anions increases the size of our atom.