iodida

Iodide, or iodide ion (I−), is the negatively charged form of iodine. It is the most common iodine species in aqueous solutions and occurs in many salts, such as potassium iodide (KI) and sodium iodide (NaI).

Iodide participates in redox chemistry: it can be oxidized to iodine (I2) by oxidants, or further to hypoiodite (OI−) and iodate (IO3−) under different conditions. In analytical chemistry, iodide is used in iodometric titrations and forms a pale yellow precipitate as silver iodide (AgI) with silver salts. It also serves as a nucleophile in organic synthesis and as an iodinating reagent under suitable conditions.

Occurrence and biology: Iodide is abundant in seawater and is part of the global iodine cycle. It is an essential micronutrient for humans and other vertebrates, required for thyroid hormone synthesis. The thyroid concentrates iodide via the sodium-iodide symporter. Deficiency can cause goiter and developmental effects; iodized salt helps prevent this.

Industrial and medical uses: iodide salts are used in nutrition supplements, antiseptics (for example povidone-iodine), and reagents in chemical synthesis. In photography, iodide contributes to light-sensitive silver halides; it remains relevant in some catalytic and stabilizing roles in various processes.

Safety: exposure to high iodide levels can disrupt thyroid function and may cause dermatitis or poisoning in sensitive individuals. People with thyroid disorders should seek medical advice before large doses. Proper storage and handling guidelines apply to iodide-containing compounds.