Complex fluorides, radon

An authoritative review on the chemistry of radon, which includes the formation of clathrate compounds, the simple and complex fluorides, ionic radon in solution, redox properties, and the various unsuccessful efforts to prepare an oxide and halides of radon other than the fluoride, was published by the most significant contributor to this field in 1983 (14). 

Chemically, radon is a noble gas. As such, it is colorless, odorless, and almost chemically inert. Although radon is not chemically active, it is interesting to note that radon is not a totally inert gas either. Studies on radon chemistry have been reported in which compounds such as clathrates and complex fluorides have been formed. Compared with the other noble gases, radon is the heaviest and has the highest melting point, boiling point, critical temperature, and critical pressure. 

Since the discovery of the first noble gas compound, Xe PtF (Bartlett, 1962), a number of compounds of krypton, xenon, and radon have been prepared. Xenon has been shown to have a very rich chemistry, encompassing simple fluorides, XeF2> XeF, and XeF oxides, XeO and XeO oxyf luorides, XeOF2> XeOF, and Xe02 2 perxenates perchlorates fluorosulfates and many adducts with Lewis acids and bases (Bartlett and Sladky, 1973). Krypton compounds are less stable than xenon compounds, hence only about a dozen have been prepared KrF and derivatives of KrF2> such as KrF+SbF, KrF+VF, and KrF+Ta2F11. The chemistry of radon has been studied by radioactive tracer methods, since there are no stable isotopes of this element, and it has been deduced that radon also forms a difluoride and several complex salts. In this paper, some of the methods of preparation and properties of radon compounds are described. For further information concerning the chemistry, the reader is referred to a recent review (Stein, 1983). 

Russian scientists (Avrorin et al., 1981, 1985) have reported that reactions of complex mixtures of radon, xenon, metal fluorides, bromine pentafluoride, and fluorine yield a higher fluoride of radon which hydrolyzes to form RnO. However, efforts to confirm these findings have been unsuccessful. In similar experiments which have been carried out at Argonne National Laboratory (Stein, 1984), it has been found that radon in the hydrolysate is merely trapped in undissolved solids centrifugation removes the radon from the liquid phase completely. This is in marked contrast to the behavior of a solution of XeO, which can be filtered or centrifuged without loss of the xenon compound. Hence there is no reliable evidence at present for the existence of a higher oxidation state of radon or for radon compounds or ions in aqueous solutions. Earlier reports of the preparation of oxidized radon species in aqueous solutions (Haseltine and Moser, 1967 Haseltine, 1967) have also been shown to be erroneous (Flohr and Appelman, 1968 Gusev and Kirin, 1971). 

Claims by Russian workers that a higher fluoride of radon, RnF4 or RnFe, can be prepared in tracer experiments by heating radon, xenon, fluorine, bromine pentafluoride, and either sodium fluoride or nickel fluoride, and converted to RnOa by hydrolysis 240) appeared to others (235) to be due to the precipitation of radon as a solid complex, which is probably [RnFJJlNiFe]. However, the precipitation of CsXeOsF from aqueous solutions results in the coprecipitation of radon, and this has been taken by the Russian group as confirmation that RnOs is the product of hydrolysis of the fluoride formed 241). Furthermore,... 

Argon (Ar) gas, for example, is over 30 times more abundant than carbon dioxide and, therefore, not rare. And xenon is not inert it s first compounds were created in 1962. When xenon (Xe) forms binary fluorides and oxides as well as fluoride complexes and oxoanions, the stability of these compounds is very low. It s reactivity is related to increasing atomic size as you go down the table, which leads to a decrease in the first ionization potentials. Xenon tetraflouride (XeF,) is made by mixing one part xenon gas to three parts fluorine gas in a container at 400 °C. Compounds have been confirmed for argon (HArF), krypton (KrF2), xenon (numerous fluorides, oxyfluorides, and oxides), and radon (RnF2). It s believed that compounds exist with helium and neon as well, though none have been experimentally proven to date. 

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