This element is used to test for starch, and at STP, it is a purple solid.
A binary compound of this element and silver undergoes a phase transition at 147 C to become a fast ion conductor. Iridium is bound to two atoms of this element and two molecules of carbon monoxide in the resting form of the catalyst for the BP Cativa process. Vicinal diols can be cleaved into aldehyde or ketone fragments by a compound with this atom in the middle. A compound containing a pentavalent atom of this element is used as a mild oxidant for alcohols and is named for (*) Dess and Martin. Treating solutions containing this element's anion with Ag+ gives a pale yellow precipitate that doesn't dissolve in excess ammonia. This element is used to test for starch, and at STP, it is a purple solid. For 10 points, name this heaviest non-radioactive halogen, found right below bromine on the periodic table.
A binary compound of this element and silver undergoes a phase transition at 147 C to become a fast ion conductor.
iodine [or I]