Oxides of the Elements

The principal oxides of the elements of this group are given in Table 25.5. 

The usual products are the oxides of the elements present in the original substance in their higher valence states. When N, Cl, Br, and I are present in the original compound, they are usually released as free elements, not as the oxides. 

Oxidation of the elements in acidic media (e.g., H2S04, HSO3F or anhydrous HF) or in liquid SO2. Suitable oxidants are provided by S20g2-, S206F2 or MF5 (M = As, Sb) ... 

Sulfur or selenium homocycles containing one (or more) exocyclic halogen substituent are prepared by the oxidation of the element with arsenic or... 

Plutonium dioxide (yellow-green to brown, cubic) is the most important oxide of the element. Almost all compounds of plutonium are converted to the dioxide upon ignition in air at about 1.000°C. 

The acidity and basicity of an oxide of an element depends on the electronegativity of that element. The greater the electronegativity the more acidic the oxide of the element, and the less the electronegativity, the more basic the oxide of the element. 

Since the electronegativity of elements decreases from top to bottom in a group, the basicity of the oxides of the elements increases and the acidity of the oxides of the elements decreases. 

Oxidation of the elements (e.g., by AsF5) in suitable solvent such as S02 or H2S04 gives a series of polyatomic cations such as [S8]2+ and [S4]2-. The later (and its Se and Te analogues) has a square-planar structure and can be regarded as a 6 p-electron ring. 

Other cationic species can be prepared by strong oxidation of the elements (e.g. with AsF3) in a suitable non-aqueous solvent. Examples include Cl+3, Br+2 and I+5 which are also known in solid salts with an ions such as AsF-6. 

A complete combustion reaction is the reaction of a compound or element with 02 to form the most common oxides of the elements that make up the compound. For example, a carbon-containing compound undergoes combustion to form carbon dioxide, C02. A sulfur-containing compound reacts with oxygen to form sulfur dioxide, S02. 

During a typical combustion reaction, an element or a compound reacts with oxygen to produce oxides of the element (or elements) found in the compound. Figure 14.2 shows an example of a combustion reactions. 

Other anionic species include the ions [Ge(S03F)6]2 and [Sn(S03F)5] formed by oxidation of the element with S206F2in HSO3F, the nitrate [Sn(N03)6]2", and SnCl5(THF)".64 There are also distorted tbp spirocyclic oxygen or sulfur chelated anions (e.g., 8-IV and 8-V) that are nonrigid in solution, oxalates [M(ox)3]2", and other carboxylates. 

It has long been known that sulfur, selenium, and tellurium will dissolve in oleums to give blue, green, and red solutions, respectively, which are unstable and change in color when kept or warmed. The colored species are cyclic polycations in which the element is formally in a fractional oxidation state. It is difficult to isolate solids from oleum solutions, and crystalline salts can be much more easily obtained by selective oxidations of the elements with SbF5 or AsF5 in liquid HF or S02,7 or with 82( 2 in HSO3F. 

The goal of the present monograph is to generalize the works carried out in this research direction. The subject of investigations is the synthesis of complex oxides of the elements ofl-Vin groups of the Periodic Table from ordinary hydroxides. For numerous hydroxides, substantial differences in their properties are observed, in particular, the differences in acid-base characteristics due to the structure of electron shells of atoms and the nature of chemical bonds. This allows one to search the definite laws governing the formation of complex oxides, and to look for correlation between the structure of initial hydroxides, their thermodynamic parameters and kinetics of mechanochemical synthesis. 

Pletnev R.N., Ivanin A.A., Kleshchev D.G. Hydrated Oxides of the Elements of IV and Vgroups. Moskva Nauka, 1986. 

This section gives a brief overview of some of the more important properties of the binary oxides of the elements. Some of the more important aspects that must be considered in evaluating a compound are its thermodynamic stability and chemical reactivity, particularly with respect to oxidation or reduction as well as reactivity with such constituents of the atmosphere as dioxygen, water vapor, and carbon dioxide, since these factors will determine the commercial availability of the compound and the need for any particular precautions in its handling or storage in the laboratory. 

The dissolution and oxidation of the elemental manganese in steel alloys to permanganate (HOMn Os) by HOIO3... 

Neil Bartlett, Valency in the Periodic Table — Concerning the Limits of Oxidation of the Elements, The Robert A. Welch Foundation Conference, Chap. X, Proc. Robert A Welch Foundation Conf. Chem. Res., XXXII Valency (1988) 259. 

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