Pentavalent ions

In the ionic implantation, a beam of trivalent ions (e.g. B+ ions), is used to produce a p+ layer. Pentavalent ions (e.g. P ions), instead, create an n+ layer. The main advantage of this technique rely in the fact that the ions penetrate the crystal only for a short distance from the surface ( 200nm). The penetration depth depends on the beam energy (25 100keV). Typical doping level is 1018 1019ions/cm3. With such a high dopant concentration, the layer becomes practically a metal. 

When an electrolyte which is without action on vanadium at ordinary temperatures (for example, dilute solutions of mineral acids, of oxalic acid, or of potassium halides) is electrolysed with a vanadium anode, a complex tetravalent vanadium ion is produced. Similarly, electrolysis at 100° C. and in molten chlorides of sodium or zinc gives rise to complex tetravalent vanadium ions. The E.M.F. in each case is found to be independent of the nature of the electrolyte. When, however, solutions of caustic soda or of caustic potash are employed, the vanadium dissolves as a pentavalent ion, irrespective of variations... 

Bismuth forms tervalent and pentavalent ions. Tervalent bismuth ion Bi3+ is the most common. The hydroxide, Bi(OH)3 is a weak base bismuth salts therefore hydrolyse readily, when the following process occurs ... 

Pentavalent. The complexation of the Pa and Np pentavalent ions by nitrate is known however, limited thermodynamic and structural data are known. For Pa, mixed hydroxo/nitrato or oxo/nitrato complexes have been proposed. The presumed structure for the Np species is Np02(N03)(H20),. 

The most prevalent form of uranium in aqueous solution is the tight yellow, fluorescent uranyl ion U02. The U cation (green in solution) can be obtained by strong reduction of U(V1), but readily oxidizes back to U02 in air. The pentavalent ion U02 can be reversibly formed by reduction of U02, but it readily disproportionates into U(IV) and U(VI). The trivalent U can be formed by reduction of U(IV) but is unstable to oxidation in aqueous solution. 

This test identifies the substance to be examined as a salt of antimony(III), Sb +, or antimony(V), Sb +. Antimony(III) and antimony(V) were formerly used in the oral treatment of intestinal worms and topically in the treatment of infections of protozoan parasites in the skin. But since especially tetrava-lent antimony is poisonous, they have generally been replaced by less toxic alternatives. At present, there are no monographs of antimony compounds in the European Pharmacopoeia. Antimony forms both tetra- and pentavalent ions, but the pentavalent is mainly found in oxides containing the antimonate ion, Sb04. Antimony(III), on the other hand, can be found as the free dissociated ion, Sb +, but, as also for example bismuth, since it reacts with water at neutral pH, forming antimonate. 

The test identifies the substance to be examined as a salt of bismuth, Several insoluble bismutii salts have foxmd use orally as antacids and topically in the treatment of skin disorders. Others have been used in the treatment of syphilis and as an amoebicide. Most of these therapeutic substances have been replaced by more modem alternatives, and reference to bismuth is currently made in only four monographs, and just one dictate method (a). Bismuth forms trivalent and pentavalent ions, but the trivalent is by far the most conunon. Most bismutii(III) and bismuth(V) forms insoluble salts, especially xmder alkaline conditions. This behavior and the insolubility of bismuth sulphide form the basis of test (a). In test (b) a colored complex between bismuth and thiourea is formed. 

The electrical conductivity of the varistor system can be improved with the addition of pentavalent ions as SbjOs [62], NbjO [1], and V2O5 [63], which act as electron donors to the crystal lattice, resulting in electron concentration and tin vacancies, as demonstrated in Eq. 22 [1,62] ... 

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