Xenon viii

All possible xenon(IV) and xenon(VI) oxyfluorides are known. Among the xenon(VIII) oxyfluorides, oifly XeOFe is not yet isolated. 

The perxenates are colorless, thermally stable solids. Anhydrous sodium perxenate can be obtained at 373 K. It decomposes at 633 K. The corresponding barium salt decomposes at about 570 K. Perxenate solutions are powerful and rapid oxidizing agents. Xenon(VIII) is reduced to xenon(VI). Oxidation processes in acid media are more effective, but they must be fast enough to compete with decomposition of the perxenate, which is also rapid in acid. 

Hydrolysis of xenon hexafluoride or tetrafluoride with a sodium hydroxide solution results in the precipitation of a stable xenon (VIII) salt, sodium perxenate, Na4XeOe, which on heating does not decompose until around 300°. Similar hydrolysis with potassium hydroxide can yield a yellow precipitate which is a mixed potassium perxenate-xenon trioxide salt, and is explosive even when damp. With more concentrated base, the much more stable hydrated perxenate may be isolated. 

Though the Gelius structure of the 4p region is particularly easy to observe in gaseous xenon (because no strong background of inelastically scattered electrons occurs) it is of obvious interest to attempt the detection in solids. The xenon(VIII) compound (153) sodium perxenateNa4Xe06 has/ (Xe 3 d) = 679.2 and 691.8 eV,... 

Xenon(VIII) oxyfluoro anions or cations have not yet been isolated. 

Salts containing the octahedral Xe(VIII) perxenate ion Xe04-g are known, and by the action of acid the tetrahedral xenon teroxide Xe04 is formed. 

Xenon reacts directly only with F2, but compounds in oxidation states from II to VIII are known, some of which are exceedingly stable and can be obtained in large quantities. The more important compounds and some of their properties are given in Table 14-2. 

Xe04 was first prepared by the reaction of concentrated sulfuric acid with xenates(VIII) at room temperature or lower. When the reaction is carried out slowly, about one-third of the xenon is converted to Xe04. The tetroxide is purified by vacuum sublimation. Xe04 is a pale yellow solid that, at 273 K, has a vapor pressure of about 33 x 10 Pa,... 

In acid or neutral solution the xenon is present as discrete XeO molecules. In basic solutions a negative ion, HXe04, is formed. In neutral or alkaline solutions the XeO slowly decomposes to xenon and oxygen. In strong base disproportionation takes place to produce per.xenates, salts of. enon(VIII). 

Since the products are perxenate (an Xe(VIII) species) and elemental xenon, this reaction is a disproportionation of the Xe(VI) species HXe04 . Oxygen is produced from a thermodynamically unstable intermediate with Xe(IV), possibly as follows ... 

Xenon hexafluoride hydrolyzes in excess dilute acid or water to produce XeOs [Xe(VI)] in solution. Hydrolysis with strong base results in the precipitation of a perxenate salt [Xe(VIII)]. Xenon hexafluoride is a fairly strong fluorinating agent, and it forms addition compounds with other fluorides such as BFs, AsF, SbFs, and alkali metal fluorides. 

Observe how in one stroke we produced octavalent and tetravalent xenon, or equivalently in this case Xe(VIII) and Xe(IV). The octavalent Xe intermediate readily adds a hydroxide to form perxenate ... 

The crystal of VII has two crystallographically independent molecules, A and B, in the PI cell. Both of the 2-ce groups of A and B take the perpendicular conformation and are contacts with each other around a pseudo inversion center. The crystal was irradiated with a xenon lamp for a week until the crystal was decomposed. The crystal analyzed by X-rays showed no change. This is because the conformation of the 2-ce group is perpendicular to the cobaloxime plane and the cavity volumes, 12.1 and 14.0 for A and B, are too small. The crystal of VIII suitable for X-ray work was not obtained. 

When the crusaders seized Constantinople in 1204 and subsequently established the Latin Empire, many Byzantine philanthropic institutions were destroyed. We know that the Western soldiers sacked the famous Sampson Xenon next to Hagia Sophia and that, as a result, it ceased to function as a medical hospital. After the restoration of the Greek state in 1261, the Sampson did not reopen its hospital wards. The ancient Panteleemon Xenon, founded in the sixth century, also lay in ruins when the emperor Michael VIII liberated Constantinople. It remained in this state until a monk named Niphon spent his private fortune to refurbish it in 1340. ... 

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