Group VIA elements

6 Group VIA Elements Oxygen group - O, S, Sc, Te, Po Table 2.9. Group VIA Properties 

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Examples of BXg-group-VIA element adducts include (i7 -Cp)2MoH2, which adds BF3, and (Tj -Cp)2WH2, which adds BF3 as well as BClj. A tensimetric titration of BF3 with (tj -Cp)2MoH2 in toluene indicates a 1 1 adduct, and (17 -Cp)2WH2 reacts with BF3 gas both in the solid state (33.6°C, 3 d) and in toluene solution, whereby (tj -Cp)2WH2 BF3 precipitates immediately. Similarly, if a (tj -... 

Sulfur vapor consists of a mixture of species that includes S8, S6, S4, and S2 (which like 02 is paramagnetic). Because the S8 molecule is nonpolar, it is soluble in liquids such as CS2 and C6H6. Selenium also consists of cyclic molecules that contain eight atoms, and tellurium is essentially metallic in character. In their vapors, several species are found that contain 2, 6, or 8 atoms. Both are useful as semiconductors, and selenium has been used in rectifiers. Because the electrical conductivity of selenium increases as the intensity of illumination increases, it has been used to operate electrical switches that open or close as a light beam is broken. Selenium was also used in light meters, but other types of meters are now available that are more sensitive. Table 15.1 gives a summary of the properties of the group VIA elements. 

By far the most common compounds containing the group VIA elements and hydrogen are those having the formula H2E, and the properties of these compounds are summarized in Table 15.2 with H20 included for comparison. The H2E compounds are extremely toxic. 

Many compounds of the group VIA elements are covalent or contain the elements as complex anions. 

There are a considerable number of well-known halogen compounds of the group VIA elements, but the majority of them are fluorides and chlorides. Table 15.4 summarizes data for most of the group VIA halides. 

There are numerous other halogen compounds of the group VIA elements as well as ionic species derived from them. Space does not permit a full review of the halogen compounds of group VIA elements, but the discussion shows much of their behavior. 

EXAMPLE 4 Figure 9-3 shows a single resonance structure for ozone. Each oxygen is assigned a 6 due to the number of valence electrons present (a Group VIA element—6 electrons). 

The nature of metal carbonyls has already been indicated (p. 159). The hexacarbonyls formed by the Group Via elements are white solids whose boiling points lie between 145° C (for Cr(CO)6) and 175° C (for W(CO)e) each of the molecules is octahedral. Since each of the metals precedes a rare gas in the Periodic Table by twelve spaces, these carbonyls are in accord with the Sidgwick-Bailey rule (p. 158). The failure of all attempts to prepare uranium hexacarbonyl, U(CO)e, was taken as an early indication that the period following radon was not an 18-membered period (a good example of reaching a correct conclusion through a somewhat questionable assumption). 

King, R. B. (1995). Inorganic Chemistry of the Main Group Elements. New York VCH Publishers. An excellent introduction to the descriptive chemistry of many elements. Chapter 6 deals with the chemistry of the Group VIA elements. 

Table 15.2 Properties of Hydrogen Compounds of Group VIA Elements...

The np configuration of the outermost ( th) shell is common to all the group VIA elements and different from the outermost configuration of the other elements. It is the cause of their similar chemical properties. 

What can be said about the oxidation numbers of the group VIA elements in oxoanions whose names have the suffix -ate ... 

Hydrides of the bcc group VIA elements Cr and Mo, but not W, are prepared by high-P techniques " . Chromium hydride is synthesized directly from Cr with Hj by keeping a thin Cr foil at 150°C under 2200 MPa for 4 h. The H/Cr atom ratio is 0.93 and the metal lattice structure hep . The hydride, therefore, is equivalent... 

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