text: a few iodine questions? could someone please tell me if iodine is flammable, combustible, and/or photosensitive, and how many isotopes it has and which one is the most common. also, what is the chemical formula of sodium. thanks, i've looked everywhere but i can't seem to find the answers. iodine is not flamable or combustible. it does combine with o2 as an iodate. iodine is not photosensitive but agi is photosensitive. there are a number of isotopes.127 is the most common. the others are less massive, in general.(because the atomic mass is 126.9)  sodium has a symbol of na. compounds have formulas, such as nai, sodium iodide.