Noble gas compound
Noble gas compounds are chemical compounds that contain at least one noble gas atom, which is attached via a covalent bond. Noble gases have a completed valence shell and therefore no tendency to compound formation. Nevertheless, there are some of noble gases connections. However, these tend to decay very in the elements and a lot of them are only stable at low temperatures. Therefore, they are also very strong oxidizing agents.
Noble gas compounds are known so far only from the four heavy noble gases argon, krypton, xenon and radon, but not of helium and neon. No inert gas compounds, the so-called inclusion complexes or clathrates, in which the noble gas atoms are only weakly bound.
Stability
In the light noble gases helium and neon, the first ionization energies are very high. It has not yet been able to reach their ionization by chemical methods, because there is no oxidant, that would be such a reaction in the situation.
For the heavier homologues, the ionization energy with increasing atomic number is steadily decreasing, so it stable compounds can be formed. Therefore, there is a noble gas compounds of the noble gases argon only to radon. From the 2006 -added, yet unnamed element 118 ( UUO ) only three atoms were generated whose chemical properties are still unknown.
When radon compounds, the stability is also limited because this element is radioactive and also the longest-lived isotope 222Rn only has a short half -life of less than 4 days.
Important compounds
Of the element, only the Krypton Kryptondifluorid KrF2 compounds have so far ( on the reaction with Lewis acid as a KrF MFn the strongest known oxidants ) and the stable only at low temperatures Kryptonbis ( pentafluororthotellurat ) Kr ( OTeF5 ) 2 is known.
Most noble gas compounds are xenon compounds. In xenon, the xenon compounds in oxidation states 2, 4, 6 and 8. Compounds as xenon fluorides, oxides, as well as xenon -nitrogen compounds, xenon -carbon compounds and complex compounds ( for example XePtF6 ) are known.
Fluoride
There are three known basic Xenon fluorine compounds:
Xenon difluoride XeF 2, Xenon tetrafluoride and xenon hexafluoride XeF4 XeF6.
Xenon difluoride and xenon tetrafluoride are linear or square-planar according to the VSEPR model. They occur monomeric. Xenon hexafluoride is square - bipyramidal ( distorted octahedral) established.
All xenon fluorides are prepared by the thermal or photochemical activation of xenon / fluorine mixtures. Which product is produced depends on the molar ratio and the reaction conditions (pressure, temperature).
→ see also: excimer laser ( unstable: F2, Xe, ArF, KrF, XeBr, XeCl, XeF )
Oxides
As oxides xenon ( VI) oxide and xenon XeO3 (VIII ) oxide XeO4 known. Both oxides are very unstable and explosive, they are strong oxidizing agents. The structure of the Xenontrioxids is tetrahedrally by the VSEPR model trigonal- pyramidal (pseudo - tetrahedral ) that the Xenontetroxids.
→ Presentation of the trioxide by complete hydrolysis of xenon hexafluoride:
More links
- The first xenon compound produced was Xenonhexafluoroplatinat XePtF6 in 1962.
- The first xenon metal compound prepared is a tetra -xenon gold ( II) cation which is an exact square-planar structure. It was synthesized by Stefan Seidel and Prof. Konrad Seppelt from the Institute of Inorganic and Analytical Chemistry at the Free University of Berlin.
- A xenon - nitrogen compound was first introduced in 1974 by DesMarteau:
- The Argonfluorohydrid ( HArF ) could be synthesized by photolysis of hydrogen fluoride in an argon matrix at 7.5 K in 2000. Evidence succeeded on the basis of new lines in the infrared spectrum. The compound is only stable at temperatures below 27 K.