Halide ions are negatively charged ions formed when halogen atoms gain an electron. The halogens include elements like fluorine, chlorine, bromine, iodine, and astatine. These ions are commonly found in various compounds, such as salts, where they bond with positively charged ions, known as cations. Halide ions play a significant role in many chemical reactions and processes. For example, sodium chloride (table salt) consists of sodium cations and chloride anions. Additionally, halide ions are important in biological systems and industrial applications, including the production of fluorinated compounds used in refrigeration and pharmaceuticals.