And oxidation state

A volt-equivalent diagram for the water-soluble nitrogen species in acidic solution is shown in Figure 6.4. It shows that the nitrate(V) ion is the least stable species, but also indicates the meta-stability of nitrous acid, which is unstable with respect to disproportionation into oxidation states + 5 and zero ... 

Group-5 elements are most stable in their maximum oxidation state +5 and therefore form pentahalides, see Figure 7. Most volatile are the pentafluorides, followed by the pentachlorides and the pentabromides. Besides the pure halides, also the oxyhalides (MOX3) are stable in the gas phase. They should be less volatile compared to the pure halides. This was confirmed experimentally for niobium, see Figure 8. 

The evidence that during the reaction of CrO with water 1dff02 is exclusively generated (219) prompted us (222, 224) to use this chromium peroxocomplex as a substrate for erythrocuprein. Stomberg and Brosset (223) showed in 1960 that the chromium ion is in the oxidation state + 5 and surrounded by four 02 groups. No evidence from X-ray crystallographic data so far was obtained for the presence of superoxide. The possibility that 02 may be formed during the aqueous decomposition of... 

The oxohalides of technetium and rhenium are more numerous than those of manganese and are not so unstable, although all of them readily hydrolyse (with dis-proportionation to [M04] and MO2 in the case of oxidation states +5 and - -6). In this resptect they may be regarded as being intermediate between the halides and the oxides which, in the higher oxidation states, are the more stable. Treatment qf the oxides with the halogens, or the halides with oxygen are common preparative methods. The structures are not all... 

Pulse radiolysis ° of aqueous solutions of xenon trioxide at pH 8-9, and of xenate, HXe04, at pH 11-13 gave unstable species with xenon in the formal oxidation states 5 and 7. Pulse radiolysis and flash photolysis of aqueous solutions of perxenate HXeOe gives xenon(IX) compounds. These show similarities to the corresponding iodine species in oxidation states 4, 6, and 8. 

Vanadium, a typical transition element, displays weU-cliaractetized valence states of 2—5 in solid compounds and in solutions. Valence states of —1 and 0 may occur in solid compounds, eg, the carbonyl and certain complexes. In oxidation state 5, vanadium is diamagnetic and forms colorless, pale yeUow, or red compounds. In lower oxidation states, the presence of one or more 3d electrons, usually unpaired, results in paramagnetic and colored compounds. All compounds of vanadium having unpaired electrons are colored, but because the absorption spectra may be complex, a specific color does not necessarily correspond to a particular oxidation state. As an illustration, vanadium(IV) oxy salts are generally blue, whereas vanadium(IV) chloride is deep red. Differences over the valence range of 2—5 are shown in Table 2. The stmcture of vanadium compounds has been discussed (6,7). 

The group oxidation state of +5 is too high to allow the formation of simple ionic salts even for Nb and Ta, and in lower oxidation states the higher sublimation energies of these heavier metals, coupled with their ease of oxidation, again militates against the formation of simple salts of the oxoacids. As a consequence the only simple oxoanion salts are the sulfates of vanadium in the oxidation states +3 and +2. These can be crystallized from aqueous solutions as hydrates and are both strongly... 

This half-reaction occurs when the anion cannot be oxidized. Examples include nitrate and sulfate anions, where the nonmetal present is already in its highest oxidation state (+5 for N, +6 for S). 

Strictly speaking the higher charge states 6+ and 5+ should be presented as oxidation states (VI) and (V). 

The most important pathway of sulfur through the atmosphere involves injection as a low-oxidation-state gas and removal as oxidation-state VI sulfate in rainwater (Fig. 13-2, paths 1, 4, 5, 6, 7, 8, 9,10,12, and 13.) Since this pathway involves a change in chemical oxidation state and physical phase, the lifetime of... 

Figure4.14 Decomposition energiesforthe Croup 11 fluorides in the oxidation state +5 (MFg — MF4 + F2) and + 3 (MF4 MF2 + F2). All data are from Ref. [207].

The oxidation states + 4 and + 5 are known for tungsten in its dithiocarbamato complexes. 

The chemistry of platinum(I) is overwhelmingly dominated by the formation of Pt—Pt bonded dimers. In addition, there are mixed oxidation state clusters and these are dealt with in Section 6.5.6. 

Earlier results regarding the kinetics and mechanism of the copper(II) catalysis are controversial. Reaction orders for [02], [Cu11], [H2A] and [H+] were reported in the following respective ranges 0.5 to 1, 0.5 to 1,0 to 1, and —2 to +1 (8). It is also disputed whether the redox cycling of the catalyst includes oxidation states +1 and +2 or +2 and +3. The discrepancies are too marked to be explained only by the differences in the experimental conditions applied. 

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