Understanding Iodide

Iodide is a negatively charged ion, or anion, with a charge of -1. It is formed from iodine, a halogen element, when it gains an electron. The chemical symbol for iodide is I^-.

Iodine itself is a halogen, a type of element that readily gains an electron to form a negative ion. Hence, the terms iodine and iodide are often used interchangeably.

IUPAC name: Iodide

Structure of Iodide - I^-

Physical Characteristics of Iodide - I^-

Chemical Behavior of Iodide - I^-

1. When iodide reacts with lead nitrate, it forms a yellow precipitate of lead iodide and sodium nitrate: Pb(NO₃)₂(aq) + 2 NaI(aq) → 2 NaNO₃(aq) + PbI₂(s).
2. If iodide reacts with chlorine, it forms potassium chloride and iodine. This is because chlorine is more reactive than iodine: 2KI + Cl₂ → 2KCl + I₂.

Applications of Iodide - I^-

• Iodide has disinfectant properties. However, its disinfectant activity decreases in cold water.
• Potassium iodide is used as a supplement to prevent iodine deficiency, which can cause goiter and mental retardation.
• Iodine-based solutions, such as povidone-iodine, are used to disinfect skin before surgery. However, iodine can cause allergic reactions and its staining can conceal redness and swelling.

Health Risks

Long-term exposure to high levels of inorganic iodide can lead to both hyperthyroidism and hypothyroidism. Overconsumption of iodide can inhibit the synthesis and release of thyroid hormone, leading to hypothyroidism and goiter.