<P> Iodine is a chemical element with symbol I and atomic number 53 . The heaviest of the stable halogens , it exists as a lustrous , purple - black metallic solid at standard conditions that sublimes readily to form a violet gas . The elemental form was discovered by the French chemist Bernard Courtois in 1811 . It was named two years later by Joseph - Louis Gay - Lussac from this property , after the Greek ἰωδης `` violet - coloured '' . </P>
where is iodine found in the periodic table
heaviest of the stable halogens