It's an atom. Atom in which our charge is zero. Well, now, suppose we take our atom and our neutral atom gains or loses electrons. Well, now we have a case in which the number of electrons is no longer equal to the number of protons. And so we're going to get a charge species called an ion. Now, whenever we're dealing with metals, be it transition metals, alkaline metals or alkaline earth metals, these guys tend to lose electrons because they can hold onto an electrons very tightly.