Fluorine Compounds - Compounds - Inorganic - Noble Gas Compounds

Noble Gas Compounds

The noble gases are generally non-reactive because they have fully filled electronic shells, which are extremely stable. Until the 1960s, no chemical bond with a noble gas was known. In 1962, Neil Bartlett used fluorine-containing platinum hexafluoride to react with xenon. He called the compound he prepared xenon hexafluoroplatinate, but since then the product has been revealed to be mixture of different chemicals. Bartlett probably synthesized a mixture of monofluoroxenyl(II) pentafluoroplatinate, +–, monofluoroxenyl(II) undecafluorodiplatinate, +–, and trifluorodixenyl(II) hexafluoroplatinate, +–. Bartlett's fluorination of xenon has been called one of the ten most beautiful experiments in the history of chemistry. Later in 1962, xenon was reacted directly with fluorine to form the di- and tetrafluorides. Since then, chemists have made extensive efforts to form other noble gas fluorides.

Having started the noble gases–fluorine compounds class, xenon is also the noble gas to have the most well-known such compounds. Its binary compounds include xenon difluoride, xenon tetrafluoride, and xenon hexafluoride, as well as their derivatives. Xenon forms several oxyfluorides, such as xenon oxydifluoride, XeOF₂, by reaction of xenon tetrafluoride with water. Its upper neighbor, krypton, is the only other one to form a well-established compound: krypton difluoride. Krypton tetrafluoride was reported in 1963, but was subsequently shown to be a mistaken identification; the compound seems to be very hard to synthesize now (although even the hexafluoride may exist). A krypton monofluoride cation has been observed.

In strong accordance with the periodic trends, radon is notably more reactive to oxidizers, including fluorine. It has been shown to readily react with fluorine to form a solid compound, which is generally thought to be radon difluoride. The exact composition is uncertain as the compound is prone to decomposition. Calculations indicate that radon difluoride may be ionic, unlike all other binary noble gas fluorides.

The lighter noble gases (helium through argon) do not form stable binary fluorides. Argon forms no binary fluoride, but reacts in extreme conditions with hydrogen fluoride to form argon fluorohydride; it is the only "stable" argon compound. Helium and neon do not form any stable chemical compounds at all. Helium forms helium fluorohydride; it has been shown to be unstable in gas phase, but there are specific conditions for which it may be stable. Neon, the least reactive element, is not now expected to form a stable compound capable of synthesis.

Ununoctium, the last currently known group 18 element, is predicted to form ununoctium difluoride, UuoF₂, and ununoctium tetrafluoride, UuoF₄, which is likely to have the tetrahedral molecular geometry. However, only a few atoms of ununoctium have been synthesized, and its chemical properties have not been examined.