What is the definition of an anion?

An anion is defined as a negatively charged ion. In the context of chemistry, ions are atoms or molecules that have gained or lost electrons and thus carry an electric charge. When an atom or molecule gains one or more electrons, it results in an excess of negative charge, which defines it as an anion. This concept is fundamental in various chemical reactions and interactions, particularly in solutions where anions play significant roles in electrical conductivity, balance of charge, and chemical stability. Understanding the characteristics of anions is essential for wastewater treatment processes, as they can be involved in the composition of wastewater and affect the behavior of other substances in treatment systems.