An atom that has gained or lost an electron and now has a net electric charge is called an ion. An ion is an atom or molecule that has a net electric charge due to the loss or gain of one or more electrons. Positive ions are formed when an atom loses an electron, while negative ions are formed when an atom gains an electron. Ions are important in a wide range of chemical processes, including the formation of ionic bonds, the conduction of electricity, and the regulation of pH.