iodineiodine

Iodine is a chemical element with the symbol I and atomic number 53. It is a lustrous, purple-black nonmetal solid at room temperature that sublimes into a violet gas when heated. Iodine is the least reactive of the halogens, fitting this pattern in terms of electronegativity and reactivity. It is the heaviest of the stable halogens, and is only slightly soluble in water.

Iodine is essential for the synthesis of thyroid hormones, which are crucial for metabolism, growth, and development. A deficiency in iodine can lead to thyroid disorders such as goiter and hypothyroidism. In many countries, table salt is iodized to prevent iodine deficiency.

Iodine has various applications. It is used as a disinfectant, a component in some photographic processes, and in the production of some dyes. In medicine, iodine solutions are used to sterilize skin before surgery. Radioactive isotopes of iodine are used in medical imaging and in the treatment of certain thyroid conditions.

Iodine was discovered in 1813 by French chemist Bernard Courtois. It was found in the ashes of seaweed, which was used to produce saltpeter. The element was named iodine from the Greek word "ioeides," meaning "violet-colored," referring to the color of its vapor.