Anomalous valency

The sum of all the cathodic partial reactions is included in e.g., oxygen reduction according to Eq. (2-17) and hydrogen evolution according to Eq. (2-19). The intermediate formation of anode metal ions of anomalous valence is also possible ... 

Polyhedral structure of the silatrane skeleton and anomalous valency state of the silicon and nitrogen atoms involved. 

The C-C distances in the Cj groups for the rare earth dicarbides are insignificantly different from their weighted average value of 1.286 A. In particular, the C-C distance in YbC2 revealed no substantial effect due to possible anomalous valence of Yb in this compound. The average value in RC2 is considerably larger than the 1.20 A in alkaline earth dicarbides (Atoji 1961, 1962, Atoji and Medrud 1959) which usually exhibit nonmetallic characteristics. 

Gomberg M (1925) Elements with anomalous valences. Chem Rev 2 301-314... 

The atomic volumes of the lanthanides, as calculated from their room-temperature lattice parameters, are shown in fig. 3. Basically this is the same plot as given by Klemm and Bommer where the lanthanide contraction is evident, and also the anomalous valence states for cerium (slightly greater than three) and europium and ytterbium (both divalent). Anomalies due to divalency are also evident in many of the physical properties and these will be duly noted throughout the chapter. The occurrence of divalency in europium and ytterbium is a striking confirmation of Hund s rule that half-filled (in the case of divalent europium with a 4f con-... 

Today the lanthanide eontraction is still one of the most important tools available to the scientist in applying systematics to the behavior of lanthanide materials. Deviations from the lanthanide contraction established for a given compound series gives a measure of anomalous valences for cerium, samarium, europiun, thulium and ytterbium (see section 3.2) which are important in evaluating the nature of these elements in valence fluctuation, heavy fermion, and spin fluctuation behaviors (see section 4.4.4). 

That the reaction really involves the formation of an inner complex salt of chromium II is shown by the fact that chromous salts react with carbazone only and not with carbazide or carbadiazone to yield a violet color. Accordingly, this is a unique instance in which the formation of a complex not only stabilizes an anomalous valence state but also brings about an anomalous redox reaction. 

Intermetallic compounds with anomalous valency states... 

Ionic compounds which contain lanthanides with a valence 2 or 4 have been known for a long time. These anomalous valence states are due to the stability of certain 4f electronic configurations, namely those of 4f°, 4f and 4f . Compounds containing tetravalent Ce, Pr and Tb and divalent Sm, Eu, Tm and Yb can be prepared. Their abundance and stability are greater for those of Ce, Eu and Yb. Some semimetallic compounds of Sm(II), Tm(II) and perhaps Pr(IV) are known, but the most studied semimetallic and intermetallic compounds are those of Ce, Eu and Yb, which are described in the following. 

Fig. 3.25 presents some dispersion curves by Brooks et al for NpN, PuN and AmN. The most pronounced changes in this series are observed for the Aj band of 5/ origin. This band becomes more and more narrow when going along this series of compounds. Finally the bands of M5/ and of higher M5/, 6d and N2p states become separated. However, the hybridisation of 5/ and N2p states remains considerable. For example, the state Tjs of NpN consists of 47% df states and 53% N2p states, while Fj of AmN consists of 46% 5/ states and 50% N2p states. The calculated and experimental values of the lattice constant versus the atomic number of the actinides are presented in Fig. 3.26. As can be seen, the experimental dependence exhibits a minimum for UN and is very different from the dependence for rare earth nitrides. The latter is monotonic and exhibits an anomaly for CeN, where Ce has an anomalous valency. While the dependence observed for rare earth nitrides can easily be explained by lanthanide compression, in the case of actinide nitrides the interpretation of such a dependence is far from trivial. The explanation proposed by Brooks et al (1984) is based on a simplified equation of state using canonical band theory. The equation takes into account only /-/ and f-p...

At the Prague Institute of Chemical Technology, F. Jirsa studied anodic oxidation of gold [15] later he published an important paper about silver electrode for a silver-iron battery [16], Jaroslav Chloupek (1899-1975), partly with V. Danes (1907-1980) and B. Danesova, studied the electrode potential in solutions of mixed manganese salts [17], the solubility and activity coefficient of Ag2S04 in some solutions [18], the ions and deviations from the approximation of Debye-Hiickel theory [19], the liquid potentials [20], and the anomalous valency effect of strong electrolytes in aqueous solution [21]. 

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