Group 16 elements binary oxides

Metal oxides containing single metalhc elements (binary oxides) and more than two metallic elements (double oxides and salts of oxoacids) are commonly used as catalysts in a variety of chemical reactions. Oxide and metallic catalysts are two major groups of industrial catalysts. In practice, most catalysts are produced from mixtures of more than two phases the phase primarily responsible for the catalysis is called the active component. 

First-order estimates of entropy are often based on the observation that heat capacities and thereby entropies of complex compounds often are well represented by summing in stoichiometric proportions the heat capacities or entropies of simpler chemical entities. Latimer [12] used entropies of elements and molecular groups to estimate the entropy of more complex compounds see Spencer for revised tabulated values [13]. Fyfe et al. [14] pointed out a correlation between entropy and molar volume and introduced a simple volume correction factor in their scheme for estimation of the entropy of complex oxides based on the entropy of binary oxides. The latter approach was further developed by Holland [15], who looked into the effect of volume on the vibrational entropy derived from the Einstein and Debye models. 

The binary representation is applicable to various other oxide materials. However, an important distinction can be made between borates and other main group element oxide systems, such as aluminates and silicates. In the latter systems cations predominantly reside at sites created by the demands of rigid anionic oxide frameworks. Although some degree of structural control may be obtained by varying cations or by use of template synthesis, the oxide frameworks of these systems tend to be relatively inflexible in comparison with... 

The periodic table is a great help in deciding whether a binary oxide is likely to form an acidic or basic solution in water. For main-group elements, it is usually sufficient to note whether the parent element of the compound is a metal or a nonmetal. Most soluble metal oxides are strong bases in water. Conversely, many nonmetal oxides react with water to give acids ... 

The reduction of phosphates by carbon is a classical method, but the purity of phosphides obtained this way can be suspect. This also holds for replacement reactions, in which a redox process between a transition metal and a metal phosphide is used for the preparation of phosphides with high thermal stabihty. Binary main-group element and transition metal phosphides hke AIP, CrP, NbP, MoP, or WP can be prepared by the reaction of the powdered metals with a melt of hthium metaphosphate LiP03. Bulk samples of transition metal phosphides hke C02P or NiMoP can be obtained via reduction of metal oxide/phosphate mixtures in a mixture of 5% H2 in N2. MoP, WP, Fc2P, M2P, FeP, and RuP can be synthesized by direct reduction of the transition metal phosphates in hydrogen atmosphere between 670 and 1320 K. ... 

Colloidal Pt/RuO c- (C5 0.4nm) stabilized by a surfactant was prepared by co-hydrolysis of PtCU and RuCls under basic conditions. The Pt Ru ratio in the colloids can be between 1 4 and 4 1 by variation of the stoichiometry of the transition metal salts. The corresponding zerovalent metal colloids are obtained by the subsequent application of H2 to the colloidal Pt/Ru oxides (optionally in the immobilized form). Additional metals have been included in the metal oxide concept [Eq. (10)] in order to prepare binary and ternary mixed metal oxides in the colloidal form. Pt/Ru/WO c is regarded as a good precatalyst especially for the application in DMECs. Main-group elements such as A1 have been included in multimetallic alloy systems in order to improve the durability of fuel-cell catalysts. PtsAlCo.s alloyed with Cr, Mo, or W particles of 4—7-nm size has been prepared by sequential precipitation on conductant carbon supports such as highly disperse Vulcan XC72 [70]. Alternatively, colloidal precursors composed of Pt/Ru/Al allow... 

Table 1 shows the main binary oxides and halides formed by transition elements of the 4d and 5d series. Comparison with the corresponding information for the 3d series (Topic H4. Table 1) shows a similar pattern, with early elements in the series forming states up to the group maximum (ZrIV,... 

The MCDF covers metals and intermetallic phases for which unit-cell parameters have been determined by diffraction methods. The database also includes hydrides and some binary oxides, but excludes elements of Groups VIIA and VIIIA. The database contains over 11000 entries, of which some 6000 have atomic coordinates, displacement parameters and site occupation data recorded. The remaining 5000 entries have been assigned to known structure types. Software for search and retrieval... 

The iota phase itself is specifically exhibited in the Ce, Pr, Tb and Cm pure binary oxides, and, in addition, oxides of this composition show a tendency for stability in the PuO and AmO. - systems. In addition, it is a very stable structure in the ternary oxides M03-3R203, where M is W, U, or Mo, and R is a rare earth element. The uranium-yttrium compound may have variable composition without phase transformation. Closely related structures having the same space group have also been prepared and characterized in the zirconia-scandia system (Zr5Sc20j3 and Zr3Sc40i2). ... 

Comparable recent detailed reviews of the actinide halides could not be found. The structures of actinide fluorides, both binary fluorides and combinations of these with main-group elements with emphasis on lattice parameters and coordination poly-hedra, were reviewed by Penneman et al. (1973). The chemical thermodynamics of actinide binary halides, oxide halides, and alkali-metal mixed salts were reviewed by Fuger et al. (1983), and while the preparation of high-purity actinide metals and compounds was discussed by Muller and Spirlet (1985), actinide-halide compounds were hardly mentioned. Raman and absorption spectroscopy of actinide tri- and tetrahalides are discussed in a review by Wilmarth and Peterson (1991). Actinide halides, reviewed by element, are considered in detail in the two volume treatise by Katzet al. (1986). The thermochemical and oxidation-reduction properties of lanthanides and actinides are discussed elsewhere in this volume [in the chapter by Morss (ch. 122)]. 

Formed by all the main-group elements except the noble gases -> Main-group binary oxides of metals are basic. 

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