An ion is an atom or molecule which has lost or gained one or more valence electrons, giving it a positive or negative electrical charge. A negatively charged ion, which has more electrons in its electron shells than it has protons in its nuclei, is known as an anion (; an-eye-on). Conversely, a positively-charged ion, which has fewer electrons than protons, is known as a cation (; cat-eye-on). An ion consisting of a single atom is called a monatomic ion, but if it consists of two or more atoms… (More on Ion)