The chemical element with atomic number 53 is iodine (I). Its name derives from the Greek word "iodes," meaning "violet," which describes the color of its vapor. Iodine is an essential element for human health, particularly for the proper functioning of the thyroid gland. While iodine is important for human nutrition, it is not considered the heaviest essential element. The heaviest essential element is generally considered to be iodine's neighboring element, xenon (Xe), which has an atomic number of 54. Xenon is a noble gas and is also found in trace amounts in the Earth's atmosphere.