Electro-affinity

The scheme of the interaction mechanism (Equation 88) testifies to an electro-affinity of MeFe" ions. In addition, MeFe" ions have a lower negative charge, smaller size and higher mobility compared to MeF6X(n+1> ions. The above arguments lead to the assumption that the reduction to metal form of niobium or tantalum from melts, both by electrolysis [368] and by alkali metals, most probably occurs due to interaction with MeF6 ions. The kinetics of the reduction processes are defined by flowing equilibriums between hexa-and heptacoordinated complexes. 

Example.—The electro-affinities of Cu and Zn in normal ( = ) solutions of their salts are - - 0 606 and — 0 493 volt, referred to the standard calomel electrode ... 

The electro-affinity of lithium is smaller than that of any of the other alkali metals, and it exhibits a greater tendency than the other alkali metals to form complex salts—e.g. the solubility of ammonia in water is raised by the addition of a lithium salt, which presumably unites with the ammonia the solubility curves of the lithium salts in water usually show more breaks than the corresponding salts of the other alkali metals owing to the formation of hydrates. Potassium, rubidium, and caesium seem to have a smaller and smaller tendency to form complex salts as the at. wt. of the element increases otherwise expressed, the electro-affinity, or the ionization tendency of the alkali metals increases as the at. wt. increases. This is illustrated by the heats of ionization. According to W. Ostwald,27 the heat of ionization per gram-atom iB... 

Unlike the results calculated for degrees of ionization from the depressions of the f.p., the values of Ostwald s constant computed from the electric conductivities of soln. of rubidium nitrate show marked deviations from constancy and they are thus constant with results with other strong electrolytes—the rubidium ion Rb and the N0V4on are among those with the greatest electro-affinities. The electrical conductivity of lithium nitrate is greater in methyl alcohdl than in water, but in... 

R. Abegg and C. Bodlander suggest that the stability of a complex depends upon the so-called electro-affinity of the ions, i.e, on the affinity of the radicles for electric charges or electrons. This can be approximately measured in terms of the electrolytic potential, on assumption that the unknown cone, of the free atoms in sat. soln. are the same for all elements. In a general way, the smaller the numerical value of the electrolytic potential (positive or negative) of a salt, the greater the tendency to form complex ions. In the further... 

Metals with widely different electro-affinities ranging from the alkalies to silver and mercury were not found to be affected much in the cold, but -when heated they gave oxides, chlorides and phosphides in various cases. 

Lithium Ion.—The colourless univalent lithium ion, Li, is characterized by the formation of salts of slight solubility with the anions of carbonic, hydrofluoric, and phosphoric acid, a distinction from the ions of the other alkali-metals, and an indication of the smaller electro-affinity of the lithium ion.12 The comparatively low electroaffinity corresponds with that of strontium, and is associated with the power of the lithium salts to form complexes with ammonia in aqueous solution, and with water to yield various crystalline hydrates. In solution in... 

The marked influence which the electro-affinity of an element has on the heat of formation of its compounds is illustrated by the diagram (Fig. 15) which is due to van t Hoff. The heats of reaction of sodium and chlorine in their compounds with S, 0, Cl, I, H, and Na are plotted as ordinates. The heats of formation of the sodium compounds diminish in approximately the same sequence as those of the chlorine compounds increase. ... 

Note The data on proton affinities (PA), electro affinities (EA) and ionization energies (IE) are available in 1988LIA/BAR, 1996NIST, and 1998HUN/LIA. 

Remark. It has to be stressed that in the syntheses of block copolymers by anionic means, the first monomer (A) to be polymerized should not exhibit an electro-affinity higher than that of the second monomer (B) (see Section 8.6). 

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