Tellurium 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. 

The physical properties of tellurium are generally anistropic. This is so for compressibility, thermal expansion, reflectivity, infrared absorption, and electronic transport. Owing to its weak lateral atomic bonds, crystal imperfections readily occur in single crystals as dislocations and point defects. 

Copper. The physical properties of pure copper are given in Table 11. The mechanical properties of pure copper are essentially the same as those for ClOl and CllO. The coppers represent a series of alloys ranging from the commercially pure copper, ClOl, to the dispersion hardened alloy C157. The difference within this series is the specification of small additions of phosphoms, arsenic, cadmium, tellurium, sulfur, zirconium, as well as oxygen. To be classified as one of the coppers, the alloy must contain at least 99.3% copper. 

Table 16.2 Some atomic and physical properties of selenium, tellurium and polonium...

Basic physical properties of sulfur, selenium, and tellurium are indicated in Table 1.3. Downward the sulfur sub-group, the metallic character increases from sulfur to polonium, so that whereas there exist various non-metallic allotropic states of elementary sulfur, only one allotropic form of selenium is (semi)metallic, and the (semi)metallic form of tellurium is the most common for this element. Polonium is a typical metal. Physically, this trend is reflected in the electrical properties of the elements oxygen and sulfur are insulators, selenium and tellurium behave as semiconductors, and polonium is a typical metallic conductor. The temperature coefficient of resistivity for S, Se, and Te is negative, which is usually considered... 

Table 1.3 Some physical properties of sulfur, selenium, and tellurium...

Table VIII lists some of the more important physical properties of TeF4. In the orthorhombic crystals, each tellurium atom is surrounded by three terminal and two bridging fluorine atoms, arranged at the apices of a distorted square pyramid. The square-pyramidal units are linked by cis-bridging atoms into endless chains with a bridge angle of 159°. The nearest intermolecular contacts to the tellurium atom are 2.94 and 3.10 A, so that there are no other significant interactions. This geometry is in accordance with the steric activity of the lone electron pair at the tellurium atom. Figure 6 shows the atomic arrangement (54).

Elemental composition H 1.56%, Te 98.44%. The gas is identified by its physical properties and measured by chemical analysis. Two most confirmatory methods recommended here are (1) GC/MS, the characteristic mass ions should be in the range 126 to 132, and (2) furnace-AA or ICP emission spectroscopic analysis for metalic tellurium. For the AA analysis, hydrogen telluride gas should be passed through water and the solution acidified and analyzed for tellurim. Hydrogen may be measured by the classical combustion method involving oxidation to form water, followed by gravimetry. 

The physical properties of the metal (Table II) resemble those of thallium, lead and bismuth, its neighbors in the Periodic Table, rather than those of tellurium, its lower homologue. The low melting and boiling points are particularly noteworthy an attempted study of the Hall effect in polonium metal has also been reported (90). In chemical properties the metal is very similar to tellurium, the most striking resemblance being in its reactions with concentrated sulfuric acid (or sulfur trioxide) and with concentrated selenic acid. The products are the bright red solids, PoSOs and... 

Physical Properties.—Tellurium is known in amorphous and crystalline forms, but it appears to differ from sulphur and selenium in... 

Te4- +4e, —0.564 V. Electronic configuration ls22s22p63s2ep63d10 — 4s24p64d105s25 pA. Other important physical properties of tellurium are given under Chemical Elements. 

Dmitri Mendeleyev (1834-1907), a Russian scientist and creator of the modern periodic table, discovered that if elements were lined up according to atomic weights and arranged in rows of 2, 8, 18, and 32, atoms with similar chemical and physical properties appeared in the same column. However, there were some exceptions. Argon and potassium were out of place. So were iodine and tellurium. Mendeleyev thought his relative weights were incorrect. 

The preparation of lithium acetylides from acetylenes and butyl lithium can be carried out in THF at 20°. The lithium acetylides react with tellurium to form lithium ethynetellurolates. These tellurolates were reacted with chloroiodomethane at — 40° to — 60 to give the corresponding chloromethyl ethynyl telluriums11. Yields and physical properties of these latter products were not reported. 

Physical Properties.—Oxygen, in common with most of the elements in the first short horizontal series of the Periodic Table, exhibits several marked contrasts with the remaining elements in its own vertical group, aud to these attention is directed in the sequel. Tellurium, again, is not typical of the group, partly in consequence of its increased... 

Pure lead has low creep and fatigue resistance, but its physical properties can be improved by the addition of small amounts of silver, copper, antimony, or tellurium. Lead-clad equipment is in common use in many chemical plants. The excellent corrosion-resistance properties of lead are caused by the formation of protective surface coatings. If the coating is one of the highly insoluble lead salts, such as sulfate, carbonate, or phosphate, good corrosion resistance is obtained. Little protection is offered, however, if the coating is a soluble salt, such as nitrate, acetate, or chloride. As a result, lead shows good resistance to sufuric acid and phosphoric acid, but it is susceptible to attack by acetic acid and nitric acid. 

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... 

Crystalline tellurium is sUvery-white and shows a metallic lustre when pure. It is rather brittle and is easily pulverized into dark grey powder. The Pauhng electronegativity of tellurium is 2.1 and its absolute electronegativity is 5.49 eV. Some other useftd physical properties are listed in Table 2. 

The elementary substances selenium and tellurium differ from sulfur in their physical properties in w ays expected from their relative positions in the periodic table. Then melting points, boiling points, and densities are higher, as shown in Table 17-1. 

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. 

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