What Is Iodine?
QUICK ANSWER
Iodine is a chemical element with atomic number 53 and the symbol I. It's a dark purple-black solid at room temperature that sublimes (turns directly into purple vapor) when heated. Iodine is an essential nutrient required by the thyroid gland to make hormones, and is used in medicine, water purification, and chemistry.
Iodine is one of the few elements that's both visually striking and biologically essential. The dark purple-black solid sublimes into violet vapor, which is how it got its name from the Greek iodes meaning 'violet.' Beyond its appearance, iodine is the element your thyroid gland absolutely requires to produce hormones that regulate metabolism. The same iodine in your salt shaker is also used to purify water and as an antiseptic on cuts.
Where is iodine on the periodic table?
Iodine has atomic number 53, the symbol I, and sits in group 17 of the periodic table among the halogens, along with fluorine, chlorine, bromine, and astatine. Its atomic mass is about 126.9. One stable isotope occurs naturally, I-127. Several radioactive isotopes have important applications, including I-131 used in cancer treatment and thyroid imaging. Iodine was discovered in 1811 by French chemist Bernard Courtois, who was extracting potassium nitrate from seaweed ash for gunpowder production when he noticed the violet vapors.
What are the properties of iodine?
Iodine is a heavy, lustrous, dark purple-black solid at room temperature with a metallic appearance. It melts at 114°C and boils at 184°C, but at normal pressure, iodine sublimes directly from solid to a violet-colored gas without melting. Density is 4.93 g/cm³. Iodine dissolves only slightly in water but readily in alcohol and other organic solvents, giving the characteristic brown color of tincture of iodine. The element is moderately reactive, less aggressive than the lighter halogens but still capable of forming many compounds with most elements.
What is iodine used for?
Medical uses dominate iodine consumption. Iodine solutions and povidone-iodine (Betadine) are used as antiseptics for skin disinfection before surgery and on wounds. Radioactive iodine-131 treats thyroid cancer and hyperthyroidism by concentrating in thyroid tissue. Potassium iodide tablets protect the thyroid from radioactive iodine during nuclear emergencies. Iodized salt prevents iodine deficiency in regions where natural iodine is scarce. Iodine compounds are also used in water purification tablets for hikers, photography (historically), pharmaceutical synthesis, and as catalysts in chemistry.
Why does the body need iodine?
The thyroid gland uses iodine to produce two hormones, T3 (triiodothyronine) and T4 (thyroxine), which regulate metabolism throughout the body. Without enough iodine, the thyroid swells into a goiter as it tries to capture more of the limited iodine available, and hormone production drops. Severe deficiency during pregnancy and childhood causes permanent intellectual disability and stunted growth. Adults need only about 150 micrograms of iodine daily, a tiny amount easily obtained from seafood, dairy, eggs, iodized salt, or seaweed. Iodized salt has nearly eliminated deficiency in most developed countries.
Iodine is the violet element that's quietly essential to human life. The dark purple solid that sublimes into colored vapor is the same element your thyroid needs to make hormones, the same element used to clean wounds, and the same element added to table salt to prevent deficiency. Few elements span such a range of practical uses.
More Chemistry Elements Questions
Mystery Question?
Mystery Question?
Mystery Question?