Oxidation stale

An unstable lower oxidation stale is found in Cd - CdCl and Cd - CdCl - AICI3 melts and may contain Cd — Cd bonds. The common co-ordination number for Cd is 6 (octahedral) although 4 and 5 co-ordination are known. 

The oxoacids of P are dearly very different structurally from those of N (p. 459) and this difference is accentuated when the standard reduction potentials (p. 434) and oxidation-stale diagrams (p. 437) for the two sets of compounds are compared. Some reduction potentials ( /V) in acid solution are in Table 12.8 (p. 513) and these are shown schematically below, together with the corresponding data for alkaline solutions. 

Table 12.9 Some lower oxoacids of phosphorus (Supcrscripl numerals in the abbreviated notation indicate oxidation stales)...

Another lechmquc fnr obtoiniag low oxidation stales is b) efecirolylk reduction uiing cyclic voltametry Some ipeciaciilar senes cnn be achieved of which, perhaps, the mewt notable is bised on lT (b no me.ms all b/ e been isolated ns solid products from solution Many other... 

Q At pH 0. the lolloping hall-reaeiions contain pairs of oxidation stales of the element. M ... 

Cornel l ihe information inio a Lalimer diagram for ihe element. M. i ami eommenl on ihe redox properlies of Ihe various oxidation stales. 

Figure 5.3 A plot of G° IF against oxidation stale for the reduction process M3+/IVT...

Q tixplain why the oxidation stale of oxygen in the oxide ion is taken to he 2. 

A In fully ionic oxides the oxygen species present is O therefore the oxidation slate of the oxygen is equal to the charge, i.e. 2. This value is taken to he the oxidation stale of oxygen in compounds that are not necessarily ionic. The oxide ion has the fully occupied valence orbitals equivalent to the electronic eonliguralion ol neon. 2j 2p<. the Group IS element at the end of the same period. 

Q Assign oxidation stales to the elements in the compounds Hj and KeSi (iron pyrites). 1... 

Table 6.1 The positive oxidation stales of the elements ol the s- and p-blocks that are stable in aqueous solution...

From Group 15 to Group 16. non-metallic behaviour takes over completely with no positive ions being stable. The + 6 state of sulfur is seen to have very poor oxidizing properties, and it is only in its concentrated form, and when hot, that sulfuric(VI) acid is a good oxidant. Hot concentrated sulfuric acid oxidizes metallic copper and is reduced to sulfur dioxide. The relative stabilities of the Se species with positive oxidation stales are considerably less than their S or Te counterparts, another example of the effect of the 3d contraction. 

I mm your understanding of the inert-pair clfeci anil the redox properties ol TI and I >. consider the apparent oxidation stale of 11 ui the compound I II and indicate what the realistic value is. flic standard reduction potential for the Tlm Tl1 couple is >. 25 V. 

Table 8.7 Oxidation stales of the aclinide elements those in red are ine most siable slates in aouecus solution in the absence ol dioxygen...

The ilillerent ranges of oxidation stales of the actinides in aqueous solution were described, discussed and compared with the much narrower ranges displayed by the lanthanide elements. 

From data given in the text, compare the standard reduction potentials of the l. 1 2 and 3 oxidation stales of the elements ("s. Bn and Lit. respectively, and their zero oxidation states. Identify the factors l ha I are responsible for the observed trend in the values of the standard potentials. 

The apparent oxidation state ofTI in Tll3 is + 3. based on the 1 idea that the oxidation stale of the more electronegative iodine atom is — l as expected lor an octet configuration. However, the mixture of Tl3 + (aq) and I (aq) is likely to cause the oxidation of iodide ion to iodine and the resulting compound is one of Tl1. i.c. Tl + (n). ... 

Step 1 The left half-cell is a standard hydrogen electrode for which we can say E = 0. In the right half-cell, mercury is in two oxidation stales. So let s write the halfreaction... 

In Ihis chapter the theories developed previously will be used 10 help correlate the important facts of the chemistry of groups 1—12 Much of the chemistry of these elements, in particular the transition metals, has already been included in the chapters on coordination chemistry (Chapters II, 12, and 13). More will be discussed in the chapters on organometaJlic chemistry (Chapter 15), clusters (Chapter 16), and the descriptive biological chemistry of the transition metals (Chapter 19). The present chapter will concentrate on the trends within the series (Sc to Zn, Y to Cd, Lu to Hg, La to Lu, and Ac to Lr), the differences between groups (Ti — Zr - Hf Cu — Ag - Au), and the stable oxidation stales of the various metals. 

For the first transition series this configuration is limited (o Cu(I) and Zndl). hut it is also exhibited by the posttransilion metals in their highest oxidation stales IGulIII). Gel IV)] The copper(l) complexes arc good reducing agents, being oxidized to Cu(II). They may be stabilized by precipitation with appropriate counterions to the extent that Cu(I) may form to the exclusion of Cu(] ) ... 

Ruthenium and osmium, unlike iron, form compounds with the metal in the -1-8 oxidation state. Can you think of a nonmetal that achieves a +8 oxidation stale in some of its compounds ... 

In addition to the +3 oxidation state seen in the homocyclic rings discussed above, phosphorus rings exist in which the +5 oxidation stale is exhibited ... 

Note that oxalic acid containing carbon in a comparable oxidation stale but not aromatic has a Ki approximately equal to A for squsne and sulfuric acids, and Kj for oxalic odd is three orders of masraiude smaller. For a difference of opinion coneeraing the aromaticity of the oxocarbon anions, see Aihura. J. J. Am. Chem. Soc. 1981.I0S. 1633-1635... 

Why do we separate clusters into two classes rather than deal with them as u single group of compounds It is primarily because they have unrelated chemistry. Metal atoms in class I have low formal oxidation states, -1 to +1. while those in class II are found in higher formal oxidation stales. +2 to +3. The transition metals on the right side of the periodic tabic (late transition metals) typically form class I clusters, while those on the left-hand side (early second and third row transition metals) tend to form class II clusters. 

Fig. 18.8 Binding energies of the Au <4/7/2) levels of gold atoms in various oxidation slates. Note that the value for RbAu and CsAu corresponds to that expected for a - I oxidation stale. [From Knechl, J., Fischer. R.. Overhof. H. Hensef. F J. Chem. Soc. Chew. Conumw. 1978. 906. Reproduced with permission. ...

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