What is an anion?

An anion is defined as a negatively charged ion. This charge arises when an atom or molecule gains one or more electrons, resulting in a surplus of electrons compared to protons. Since electrons carry a negative charge, the overall charge of the atom or molecule becomes negative, thus classifying it as an anion.

For example, when a chlorine atom gains an electron, it becomes a chloride ion (Cl⁻), showcasing the typical behavior of nonmetals that tend to gain electrons to achieve a stable electron configuration. This gaining of electrons is a key characteristic of how anions form. Other types of ions include cations, which are positively charged and are formed when atoms lose electrons, as well as neutral ions that have an equal number of protons and electrons, resulting in no net charge. Understanding these differences is crucial for grasping the fundamentals of ionic bonding and reactions in chemistry.