Monoatomic cations

The Global HSAB Principle Stabilization of Endohedral Complexes of Cgo> Si60 and Ge60 with Monoatomic Cations and Anions... 

For the first time, a systematic uniform ab initio study of endohedral complexes of C60, Si60 and Ge60 with monoatomic cations (Li+, Na+, K+ and Rb+) and anions (F-, Cl% Br and P) was performed. The 3-21 G level (3-21+G for the anions) was used. This could be achieved by application of the multiplicative integral approximation [86], as implemented in the program BRABO [87]. The sequence studied for the cages bears a close resemblance with isomorphic substitution in zeolites modifying its catalytic activity via bridging hydroxyls. 

Names of monoaronnc cations. Monoatomic cations are named by adding in parentheses after the lunie of the element (either the appropriate chaige number followed by the plus sign or the oxidation number (Roman numeral)] followed by the words cation or ion ... 

The thermodynamic ch2uacteristi( of monohydration of monoatomic cations are listed in Table 12. The AE values for all the cxnnplexes were obtained using extended basis sets for details see Ref. For the majority of the complexes studied,... 

IR-5.2 Stoichiometric names of elements and binary compounds IR-5.3 Names of ions and radicals IR-5.3.1 General IR-5.3.2 Cations IR-5.3.2.1 General IR-5.3.2.2 Monoatomic cations IR-5.3.2.3 Homopolyatomic cations IR-5.3.2.4 Heteropolyatomic cations IR-5.3.3 Anions IR-5.3.3.1 Overview IR-5.3.3.2 Monoatomic anions IR-5.3.3.3 Homopolyatomic anions IR-5.3.3.4 Heteropolyatomic anions IR-5.4 Generalized stoichiometric names... 

The name of a monoatomic cation is that of the element with an appropriate charge number appended in parentheses. Unpaired electrons in monoatomic cations may be indicated using a radical dot, i.e. a centred dot placed in front of the charge, preceded by a number if necessary. 

The proton is formed from the lightest element in the periodic table and has the smallest ionic size. It also has a special relationship to the most common polar solvent, namely, water. These two facts combine to give this ion the highest mobility in water, approximately 10 times that of the Li ion, which is the next larger monoatomic cation. In order to understand these observations one must develop a picture of how the proton is incorporated in the structure of protic solvents. 

Another way of examining the mechanism of proton transfer is by comparing its temperature dependence with that of other monoatomic cations. Plots of the molar conductance of three cations, namely, H, Li, and K, on a logarithmic scale are shown as a function of reciprocal temperature in the range 5-55°C in fig. 6.14. Excellent linear plots are found from which an energy barrier associated with the process may be calculated. Using a simple Arrhenius expression, the temperature dependence of X,- for a small temperature interval is given by... 

Chapter 29 summarizes the heats of formation of atoms, inorganic and organic radicals, and monoatomic cations or anions in the gas-phase. 

Table 1. Metal-molten salt systems in which solid, sub-valent compounds with metal-metal bonds have been synthesized by symproportionation or similar reactions. The many sub-halides of gallium and indium have been omitted. These compounds contain either sub-valent monoatomic cations e.Lj. (Ga )(GaCl4 )l > and (In )(Cl )] " and/or ligand-stabilized metal-metal bonded anions (Ga+)2(Ga2X6- ), X = Br, For a review of the sub-valent chemistry of the group...

Unfortunately, for monovalent monoatomic cations the radius varies only between 0.59 for tetrahedrally coordinated Li " and... 

In order to increase the range of cation size it is possible to replace the monoatomic cations by polyatomic inorganic complexes or by organic cations. For instance, silicates containing... 

Tab. 2.3 Absolute electronegativities and absolute hardnesses for monoatomic cations [204].

Finally, a classification of the individual ions is only possible in a rough and incomplete way. Monoatomic cations can be arranged according to the number of electrons and are referred to as d"-cations (e.g. alkali metal cations then are d -cations). Cations such as [R4N], or [RsS]" have their charges shielded by... 

It is for avoiding hydrolysis, that in many experiments polyvalent complex cations are to be preferred in place of polyvalent monoatomic cations. 

This choice of cations seems afterwards not to have been an adequate one. For as we saw in 2 i (p. 291) complex ions, by their inability to polarise the ionised groups, behave in a different way from the small monoatomic cations which have this property. 

For increase in valency of small monoatomic cations may have as a result in sulphate colloids, that reversal of charge is shifted to higher concentrations and flocculation becomes more difficult. 

Indeed carrageen flocculates with Co(NH3)complex cation), but not with La(NOs)3 (monoatomic cation). 

Another problem that is frequently encountered is to know what the appropriate charge can be on the ions under consideration. For monoatomic cations and anions, the common charges are called oxidation numbers, and they can often be identified on a periodic table (see Chapter 4). Polyatomic ions are more challenging and often must be derived from the oxidation numbers of the underlying monatomic components. Knowing some rules to determine the oxidation numbers of elements will allow you to calculate the charge for polyatomic ions. 

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