Group xenon

Survey and account for the group characteristics and trends in the elements of Group O (He-Rn). Outline the preparation and stereochemistry of xenon tetrafluoride. 

A likely exit path for the xenon was identified as follows. Different members of our research group placed the exit path in the same location and were able to control extraction of the xenon atom with the tug feature of the steered dynamics system without causing exaggerated perturbations of the structure. The exit path is located between the side chains of leucines 84 and 118 and of valine 87 the flexible side chain of lysine 83 lies just outside the exit and part of the time is an obstacle to a linear extraction (Fig. 1). 

Noble gases (Section 1 1) The elements in group VIIIA of the penodic table (helium neon argon krypton xenon radon)... 

Derivatives. The nonmetaHic inorganic derivatives of fluorosulfuric acid are generally made indirectly, although complex fluorosulfates of the Group 15 (V) elements and of xenon can be made directly (85,86), as can the NO" and NO" 2 salts (26,27). 

The existence of neon (Greek neos, new) was predicted, as was the existence of heavier members of the group. In 1898 krypton (Greek kTyptos, hidden) was discovered by spectroscopic examination of the residue from a sample of Hquid air. Neon was discovered in the same year. A month later, xenon (Greek xenos, strange) was isolated from the residue left after distillation of krypton. 

Pure Elements. AH of the hehum-group elements are colorless, odorless, and tasteless gases at ambient temperature and atmospheric pressure. Chemically, they are nearly inert. A few stable chemical compounds are formed by radon, xenon, and krypton, but none has been reported for neon and belium (see Helium GROUP, compounds). The hehum-group elements are monoatomic and are considered to have perfect spherical symmetry. Because of the theoretical interest generated by this atomic simplicity, the physical properties of ah. the hehum-group elements except radon have been weU studied. 

Except for helium, all of the elements in Group 18 free2e into a face-centered cubic (fee) crystal stmeture at normal pressure. Both helium isotopes assume this stmeture only at high pressures. The formation of a high pressure phase of soHd xenon having electrical conductivity comparable to a metal has been reported at 33 GPa (330 kbar) and 32 K, and similar transformations by a band-overlap process have been predicted at 15 GPa (150 kbar) for radon and at 60 GPa (600 kbar) for krypton (51). 

Russian exports of hehum-group gases. Prices ia 1990 were 120/m forNe, 700-800/m for Kr, and 5, 750-8, 750/m for xenon. 

Derivatives in Which Xenon is Bonded to Polyatomic Groups. 

Xenon Bonded to Nitrogen. Several ligand groups form compounds containing xenon-nitrogen bonds (12). The first xenon-nitrogen... 

Xenon Bonded to Carbon. A number of stmcturally well-characterized compounds containing Xe—C bonds are known. In all cases these occur as colorless salts of xenonium cations, R—Xe" where R is a fluorophenyl or alkynyl group. The formation of the pentafluorophenylxenon(II) cation, CgFgXe+ [121850-39-3] (-30W) and CHgC N (0°C) solutions with the anions B(C3F3)3F [121850-40-6], B(CgFg) 2F- [123168-25-2], and... 

On the other hand, oxidizing fluonnating agents like silver difluoride, xenon difluoride, or bromine trifluoride replace one chlorine group and then cleave the sulfur-nitrogen bond [56],... 

It follows from the preceding discussion that the unbranched H bond can be regarded as a 3-centre 4-electron bond A-H B in which the 2 pairs of electrons involved are the bond pair in A-H and the lone pair on B. The degree of charge separation on bond formation will depend on the nature of the proton-donor group AH and the Lewis base B. The relation between this 3-centre bond formalism and the 3-centre bond descriptions frequently used for boranes, polyhalides and compounds of xenon is particularly instructive and is elaborated in... 

Pure NI3 has not been isolated, but the structure of its well-known extremely shock-sensitive adduct with NH3 has been elucidated — a feat of considerable technical virtuosity.Unlike the volatile, soluble, molecular solid NCI3, the involatile, insoluble compound [Nl3.NH3] has a polymeric structure in which tetrahedral NI4 units are comer-linked into infinite chains of -N-I-N-I- (215 and 230 pm) which in turn are linked into sheets by I-I interactions (336 pm) in the c-direction in addition, one I of each NI4 unit is also loosely attached to an NH3 (253 pm) that projects into the space between the sheets of tetra-hedra. The stmcture resembles that of the linked Si04 units in chain metasilicates (p. 349). A further interesting feature is the presence of linear or almost linear N-I-N groupings which suggest the presence of 3-centre, 4-electron bonds (pp. 63, 64) characteristic of polyhalides and xenon halides (pp. 835-8, 897). 

The stability of the electronic configuration is indicated by the fact that each element has the highest ionization energy in its period, though the value decreases down the group as a result of increasing size of the atoms. For the heavier elements is it actually smaller than for first-row elements such as O and F with consequences for the chemical reactivities of the noble gases which will be considered in the next section. Nuclear properties, particularly for xenon, have been exploited for nmr spectroscopy and Mdssbauer... 

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