Dipositive ions

Recently, Muha (83) has found that the concentration of cation radicals is a rather complex function of the half-wave potential the concentration goes through a maximum at a half-wave potential of about 0.7 V. The results were obtained for an amorphous silica-alumina catalyst where the steric problem would not be significant. To explain the observed dependence, the presence of dipositive ions and carbonium ions along with a distribution in the oxidizing strengths of the surface electrophilic sites must be taken into account. The interaction between the different species present is explained by assuming that a chemical equilibrium exists on the surface. 

This issue has been investigated using amalgam cathodes, and the indications are that the cryptand has negligible influence on the rate of incorporation of a sodium ion into the amalgam (Chen et ai, 1991 Doan et al, 1991). One of the most interesting applications of the cryptands is that they increase the mobility of dipositive ions in polymer electrolytes (Chen and Shriver, 1991). 

STPP is used primarily as a builder for detergents, including dishwashing detergents (45%) and industrial and institutional detergents (31%). It also has food uses (13%). Up to 1988 it was in the top 50 chemicals because of its powerful ability to sequester dipositive ions in hard water, but it causes eutrophication of lakes and has been replaced in most detergents by other compounds. 

In general, it is observed that the charges on simple positive ions are limited to a maximum of three even if an inert gas configuration is not reached. Thus the elements of the transition series all may lose two electrons (the s electrons are lost first) to give dipositive ions in ionic compounds, and a number of them give -1-3 ions. Similarly, as a rule, the lanthanide... 

The alkaline earth metals undergo the same kinds of redox reactions that the alkali metals do, but they lose two electrons rather than one to yield dipositive ions, M2+. Because their first ionization energy is larger than that of alkali metals (Figure 6.3), the group 2A metals tend to be somewhat less reactive than alkali metals. The general reactivity trend is Ba > Sr > Ca > Mg > Be. 

The ease of oxidation of polycyclic aromatic hydrocarbons in the gas phase481 as well as in solution is well-documented.482 195 In strong acid solutions, monopositive radical ions and/or dipositive ions, also known as oxidation dications, have been reported.271,494,495 Similar species have been observed in anodic oxidations of... 

Sodium triphosphate is used almost solely in one type of product detergents. Some detergents contain up to 50% by weight sodium triphosphate. It has the unique property of complexing or sequestering dipositive ions such as calcium (Ca2+) and magnesium (Mg2+) that are present in water. Tide is an example of a phosphate detergent that has been used for at least 5 decades. 

Dewar and Rona 37> have reported the appearance of very intense peaks due to doubly charged ions in the mass spectrum of 1,3-dimethyl-2-phenyl-diazaboracyclopentane. The ready formation of dipositive ions at relatively low ionizing potentials was interpreted to indicate an unusual stability of the ions. 

The loosely hydrated ions of the alkali metals show practically no acidic character, but certain loosely hydrated mono and dipositive ions of the heavy metals (for example, Ag+ and Hg2+) are sometimes conveniently regarded as acids in the Lewis scheme. The reaction between Ag+ and ammonia may be considered an acid-base reaction ... 

The green Mo3 cluster shows three H resonances in the ratio 1 10 5. The peak of area one (58.9, CDC13) is in the range associated with metal formyls (34) and there are two equivalent and one different Cp groups. The carbonyl stretches of the M03 cluster occur at 1763 and 1713 cm-1. The mass spectrum shows a series of Mo3 patterns starting at m/e = 580 with consecutive loss of 5 carbonyls, and a series of strong peaks due to dipositive ions corresponding to the monopositive series 524, 496, 468, and 440. 

In aqueous solution, lanthanides are most stable in the tripositive oxidation state, making them difficult to separate and purify. The preference for this oxidation state is due in part to the energy of the 4f electrons being below those of the 5d and 6s electrons (except in the cases of La and Ce). When forming ions, electrons from the 6s and 5d orbitals are lost first so that all Ln + ions have [Xe] 4f electronic configurations. Under reducing conditions, certain lanthanides (europium, samarium, and ytterbium) can be stable as dipositive ions, and cerium can adopt a +4 oxidation state (5). 

If the acetate is rich in europium or ytterbium, the yellowish or greenish colors of the dipositive ions may develop in solution. Similarly, material rich in samarium may give a reddish-brown solution. With material poor in these elements, color development indicates sodium exhaustion and solution of the lanthanon amalgam. 

The group 2A elements (the alkaline earth metals) have higher first ionization energies than the alkali metals do. The alkaline earth metals have two valence electrons (the outermost electron confignration is ns ). Because these two s electrons do not shield each other well, the effective nuclear charge for an alkaline earth metal atom is larger than that for the preceding alkali metal. Most alkaline earth compounds contain dipositive ions (Mg +, Ca, Sr, Ba +). The Be ion is isoelectronic with Li and with He, Mg is isoelectronic with Na and with Ne, and so on. 

The standard reduction potential of the No +/No + couple in aqueous solution was estimated by Silva and coworkers (28) from the extractibility of No after treatment with a variety of oxidants. The distinction between No + and No + was made on the basis of the affinity of the extractant, bis(2-ethylhexyl) phosphoric acid, for highly-charged cations. In 0.1 M acid, mono- and dipositive ions are poorly extracted, whereas the tri-and tetrapositive ions are strontly absorbed in the extractant. 

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