An ion is an atom or molecule that has a net electrical charge because it has gained or lost one or more electrons. Ions can be either positively charged, known as cations (which have lost electrons), or negatively charged, known as anions (which have gained electrons). Ions play a crucial role in various chemical reactions, biological processes, and are present in many substances including salts, acids, and bases.
The word "ion" comes from the Greek word "ion," which means "going" or "that which goes." This reflects the property of ions to move towards electrodes when subjected to an electric field.