Complex sentence: Astatine is known to react with its lighter homologues iodine, bromine, and chlorine in the vapor state; these reactions produce diatomic interhalogen compounds with formulas AtI, AtBr, and AtCl.
Split into simpler sentences: Astatine is known to react with its lighter homologues iodine, bromine, and chlorine in the vapor state. These reactions produce diatomic interhalogen compounds with formulas AtI, AtBr, and AtCl.