Tellurium compounds physical properties

Inorganic Compounds. Inorganic selenium compounds are similar to those of sulfur and tellurium. The most important inorganic compounds are the selenides, haUdes, oxides, and oxyacids. Selenium oxidation states are —2, 0, +1, +2, +4, and +6. Detailed descriptions of the compounds, techniques, and methods of preparation, and references to original work are available (1—3,5,6—10, 51—54). Some important physical properties of inorganic selenium compounds are Hsted in Table 3. 

Because the element is so rare, highly radioactive, and extremely expensive, classical chemical methods cannot be utilized in the study of its organometallic chemistry. Hence, one does not find any published information on the synthesis, physical properties, or spectroscopic characteristics of organopolonium compounds. It would be reasonable to make the assumption that the organic chemistry of polonium should parallel that of tellurium, the element just above it... 

The subhalides of tellurium are an especially important class of solid state compounds, and they have been the subject of intensive studies, so that a rather complete picture of their chemistry and their properties has been obtained in recent years. Because of their high tellurium content they contain fragments of the homonuclear tellurium chains their modified tellurium structures are of great current interest with respect to possibly significant physical properties. Consequently, the results of various investigations on the synthesis of the compounds, on phase analysis by thermal methods, on crystal growth, on the structures, on spectroscopic, thermodynamic, optical, photoelectric, electrochemical properties have been reported in the last two decades. In a comprehensive review (237) all significant results are reported and discussed in detail so that the present chapter will be restricted to some selected and chemically important features. 

Elemental composition Te 79.95%, O 20.05%. The compound can be identified by its physical and x-ray properties. Tellurium content may be measured by digesting the dioxide in HCl or aqua regia, diluting the solution, and analyzing by AA or ICP. 

Selenium and tellurium arc generally considered rare elements and are not found in abundance each, however, has a claim to special interest. The peculiar electrical properties of selenium appeal especially to the physical chemist, but the compounds of this element are of growing importance, especially in their application to the glass industry. Both selenium and tellurium offer attractive fields for research. In the case of tellurium, owing to what had been considered an erroneous value for the atomic weight, the very considerable amount of work done in the past has been too much confined to one direction interest in the chemistry of tellurium appears now to be widening, however. 

The physical NMR properties of sulfur, selenium, and tellurium are given in Table 1, and as with other groups of the Periodic Table there are expected to be considerable parallels between the chemical aspects of the NMR behavior of these elements (and indeed with oxygen too). In practice the problems associated with S NMR have restricted the types of compound studied, and it is not yet appropriate to combine the treatment of all three. However, the more recent work has served mainly to confirm the similarities of selenium and tellurium referred to previously," and so these two elements are considered together. There is a brief review of S NMR," and there are several of Se and Te NMR." ... 

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