A chloride ion is a negatively charged ion, or anion, formed when a chlorine atom gains an electron. It has the chemical symbol Cl⁻ and is commonly found in nature, especially in salt, where it pairs with sodium to form sodium chloride or table salt. Chloride ions play a crucial role in maintaining the balance of fluids in the body and are essential for various biological processes. In addition to its biological importance, chloride ions are widely used in industrial applications. They are involved in the production of chemicals, such as hydrochloric acid, and are used in water treatment to help disinfect and purify water. Their presence is vital for both environmental and human health.