Compounds of other noble gases

No krypton compounds come out to be thermodynamically stable, but KrF₂ can be complete from the elements in an electric discharge at extremely low temperatures, and some compounds of the cationic species [KrF]⁺ and [Kr₂F₃]⁺ are also known. Like the ionization energy of Kr is higher than whcih of Xe, the lower stability of krypton compounds is supposed from the bonding models depicted in structures 1 and 2, in which Xe carries a formal positive charge.

Reactions that are performed at very low temperatures have succeeding in making a range of molecules which have actually extremely low barriers to decomposition and so are not even kinetically stable at room temperature. Usual is the triatomic molecule HArF, where it come into existence that the H-Ar bond is covalent but that the Ar-F bond has a high degree of ionic character: so formulation [HAr]⁺ F^- may be suitable. It is supposed to be unstable according to Ar+HF by around 570 kJ mol^-1, and the activation barrier to decomposition might  be only 25 kJ mol^-1.