stable isotope of iodine
There are 37 known isotopes of iodine (I) from 108I to 144I; all undergo radioactive decay except 127I, which is stable. Iodine is thus a monoisotopic element. Its longest-lived radioactive isotope, 129I, has a half-life of 15.7 million years, which is far too short for it to exist as a primordial nuclide.
Iodine is a bluish-black, lustrous solid that mainly occurs in. nature as stable iodine-127. A small amount of radioactive iodine-129 is. produced naturally in the upper atmosphere by the interaction of high-. energy particles with xenon. Iodine volatilizes at ambient temperatures into. a pretty blue-violet gas with an irritating odor.