Iodide ions are negatively charged ions formed when iodine gains an electron. They are represented by the chemical symbol I⁻ and are commonly found in various compounds, including salts. Iodide is essential for human health, particularly for the production of thyroid hormones, which regulate metabolism. In nature, iodide ions are often present in seawater and certain minerals. They can also be found in iodized salt, which is used to prevent iodine deficiency in populations. Additionally, iodide ions play a role in various chemical reactions and are used in medical imaging and treatments involving iodine.