 The instability of Rn(VIII) is due to the relativistic stabilization of the 6s shell, also known as the inert pair effect.Radon reacts with the liquid halogen fluorides ClF, ClF3, ClF5, BrF3, BrF5, and IF7 to form RnF2.In halogen fluoride solution, radon is nonvolatile and exists as the RnF+ and Rn2+ cations; addition of fluoride anions results in the formation of the complexes and , paralleling the chemistry of beryllium(II) and aluminium(III).