IodidIonen

Iodidionen are the chemical anion with the formula I−, formed when iodine gains one electron. They occur in solution as part of iodide salts such as sodium iodide (NaI) and potassium iodide (KI). Iodide salts are typically soluble in water, and the iodide ion itself is colorless in aqueous solution.

Chemically, iodidionen act as reducing agents and are readily oxidized to elemental iodine (I2) by oxidizing agents such as chlorine, bromine, hydrogen peroxide, or hypochlorite. The oxidation process I− → 1/2 I2 is common in redox reactions. In organic synthesis, iodide can also function as a nucleophile in substitution reactions.

Iodide is abundant in seawater and marine organisms. It is essential for vertebrate thyroid hormone synthesis, with iodine intake linked to the production of thyroxine (T4) and triiodothyronine (T3). To prevent deficiency, iodide is added to table salt (iodized salt) and other foods in many countries. In industry and laboratories, iodide salts are used as reagents, in photography and cloud seeding contexts (via silver iodide), and in iodometric titrations, where the oxidant’s amount is determined by the amount of iodine produced or liberated.

Safety considerations are important. Iodide compounds are generally of low to moderate toxicity, but excessive intake can disrupt thyroid function and cause other health issues. Concentrated iodide solutions can irritate eyes and skin. They should be handled with appropriate precautions, stored away from strong oxidizers, and disposed of according to local regulations.