 Extrapolation down the noble gas group would suggest also the possible existence of RnO, RnO2, and RnOF4, as well as the first chemically stable noble gas chlorides RnCl2 and RnCl4, but none of these have yet been found.Radon carbonyl (RnCO) has been predicted to be stable and to have a linear molecular geometry.The molecules and RnXe were found to be significantly stabilized by spin-orbit coupling.