Lasted edited by Andrew Munsey, updated on June 15, 2016 at 2:05 am.
An ion is an atom or group of atoms that normally are electrically neutral and achieve their status as an ion by loss or addition of one or more electrons. The simplest ions are the proton (a hydrogen ion, H+, positive charge), and alpha particle (helium ion, He2+, consisting of two protons and two neutrons) . A negatively charged ion, which has more electrons in its electron shells than it has protons in its nuclei, is known as an anion (pronounced [?æna??n] an-eye-on) due to its attraction to anodes. A positively-charged ion, which has fewer electrons than protons, is known as a cation (pronounced [?kæta??n] cat-eye-on) due to its attraction to cathodes. An ion consisting of a single atom is called a monatomic ion, and an ion consisting of multiple atoms is called a polyatomic ion. Larger ions containing many atoms are called molecular ions. The process of converting electrically neutral atoms or molecules into ions and the state of being ionized is called ionization. The recombining of ions and electrons to form neutral atoms or molecules is called recombination. A polyatomic anion that contains oxygen is sometimes known as an oxyanion .