The inert pair effect on heavy noble gases: insights from radon tetroxide

A quantum chemical survey of radon and xenon tetroxides (NgO 4 , Ng = Xe, Rn) is reported herein. The intermediate species, which are formed in their explosive decomposition back to their elemental states (Ng and O 2 ), were also studied and their energetics were compared. While T d symmetric RnO 4 has a minimum energy structure, its standard enthalpy of formation is 88.6 kJ mol −1 higher than for XeO 4 . The reason for this higher instability lies in what is known as the inert pair effect. This work establishes that the high-valent chemical trends of the sixth period of groups 13-15 are indeed extended to group 18. The decomposition of noble gas tetroxides and associated formal oxidation states. Studying the energetics of tetroxides through quantum chemistry provides new insight into noble gas properties.