Atoms often gain and lose electrons, giving them a negative or positive electrical charge. These charged atoms are .

Atoms that gain or lose electrons and acquire an electrical charge are known as ions. When an atom loses one or more electrons, it becomes positively charged and is called a cation. Conversely, when an atom gains one or more electrons, it becomes negatively charged and is known as an anion.

This process of gaining or losing electrons often occurs during chemical reactions. For example, when sodium (Na) loses an electron, it forms sodium ion (Na⁺), which is a cation. On the other hand, when chlorine (Cl) gains an electron, it forms chloride ion (Cl⁻), which is an anion. These ions play essential roles in various chemical processes, including the formation of salts and the conduction of electricity in solutions.

Thus, the formation of ions is crucial in understanding chemical bonding, reactions, and the properties of substances in both solid and aqueous states.