Tellurium selenium—oxygen bonds

Fig. 13 is a drawing of electron-domain models of some Group VI hexafluorides. Open circles represent the electron-pairs of four of the six bonds to fluorine atoms in a Lewis, single-bond formulation of these molecules. Solid circles represent the atomic cores of oxygen, sulfur, selenium, tellurium, tungsten, and uranium (core radii, in hundreths of A, 9, 29, 42, 56, 62, and 80 2>, respectively). These hexafluorides are, in order, non-existent, extra-ordinarily unreactive, hydrolyzed slowly, hydrolyzed completely at room temperature in 24 hours, hydrolyzed readily, and hydrolyzed very rapidly. 

The platinum metal chalcogenides in general are easier to prepare than the corresponding oxides. Whereas special conditions of temperature and pressure are required to prepare many of the oxides, the platinum metals react most readily with S, Se, and Te. A number of additional differences concerning the chemistry of the chalcogenides and the oxides are summarized as follows The metal—sulfur (selenium, tellurium) bond has considerably more covalent character than the metal-oxygen bond and, therefore, there are important differences in the structure types of the compounds formed. Whereas there may be considerable similarity between oxides and fluorides, the structural chemistry of the sulfides tends to be more closely related to that of the chlorides. The latter compounds... 

Diaryl ditellurium compounds, when heated in pyridine, ethanol, or acetic acid with selenium dioxide, produced the corresponding bis[aryltelluro] selenium and derivatives of these compounds with oxygen bonded to tellurium and selenium4. 

In the first section of this chapter some of the properties of the elements hydrogen, carbon, nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulfur, selenium, tellurium, fluorine, chlorine, bromine, and iodine are described. The following sections are devoted to some of their compounds with one another, especially the single-bonded normal-valence compounds. Compounds of nonmetals with oxygen are discussed in the following chapter. 

We have already noted that the properties of the elements in Group VI show the characteristic trends that we have come to expect on descending a Group. The elements become more metallic in character oxygen is a covalently bonded gaseous diatomic molecule sulfur is a solid containing Sg molecules and is an insulator selenium (non-metal) and tellurium (semi-metal) are semiconductors with polymeric structures polonium is a metal. The compounds of selenium, tellurium and pollonium also illustrate the inert pair effect and a tendency to higher coordination numbers. 

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