Relation to ion size

Table 8-3 shows the lattice energies of some ionic compounds. Examine the lattice energies of RbF and KF. How do they confirm that lattice energy is related to ion size Look at the lattice energies of Sr CI2 and AgCl. How do they show the relationship between lattice energy and the charge of the ions involved ... 

The kinetics of the exchange reaction in powdered vermiculite were studied by K ay and Wild [1961, 1962], who have shown that the order of the rate of exchange against Na is, for the alkaline earths, directly related to the entropy of hydration of the ion and, for a substituted ammonium series, inversely related to ion size and energy of activation. The kinetics resembles that in strong-acid resins in giving a similar diffusion coefficient, the same order of activation energy, and the same relationship between rate and ion size. 

Another property that is closely related to electronegativity and position in the periodic table is polarizability. Polarizability is related to the size of atoms and ions and the... 

Failure of these reactions to follow the third-order law over the earlier portion of the reaction seems to be due to the pronounced changes in the characteristics of the medium with the disappearance of so many hydroxyl and carboxyl groups —changes to which an ion-catalyzed reaction should be sensitive. Whatever the exact cause of this behavior may be, it is typical of simple esterifications as well as of those which bring about polymer formation and is not therefore in any way related to the sizes of the reacting molecules. The similarity in the courses followed by mono- and by polyesterifications provides direct evidence for nondependence of reactivity on molecular size. 

Intense ion-ion interactions which are characteristic of salt solutions occur in the concentrated aqueous solutions from which AB cements are prepared. As we have seen, in such solutions the simple Debye-Hiickel limiting law that describes the strength goes up so the repulsive force between the ions becomes increasingly important. This is taken account of in the full Debye-Hiickel equation by the inclusion of a parameter related to ionic size and hence distance of closest approach (Marcus, 1988). 

The effect of the phospholipids on the rate of ion transfer has been controversial over the last years. While the early studies found a retardation effect [6-8], more recent ones reported that the rate of ion transfer is either not retarded [9,10] or even enhanced due to the presence of the monolayer [11 14]. Furthermore, the theoretical efforts to explain this effect were unsatisfactory. The retardation observed in the early studies was explained in terms of the blocking of the interfacial area by the phospholipids, and therefore was related to the size of the transferring ion and the state of the monolayer [8,15]. The enhancement observed in the following years was attributed to electrical double layer effects, but a Frumkin-type correction to the Butler Volmer (BV) equation was found unsuitable to explain the observations [11,16]. Recently, Manzanares et al. showed that the enhancement can be described by an electrical double layer correction provided that an accurate picture of the electrical double layer structure is used [17]. This theoretical approach will be the subject of Section III.C. 

The heat of hydration of an ion is related to its size and charge (see Chapter 7). However, in this case the aqua complex that is formed causes the d orbitals to be split in energy, and if the metal ion has electrons in the d orbitals, they will populate the t2g orbitals, which have lower energy. This results in... 

It was also mentioned by McLean et al. that ions and polar solvent molecules must necessarily diffuse across thin amorphous fluorocarbon or interfacial regions between swollen polar domains. However, all of this does not require the need for channels with diameters of 10 A that are coated with SOs groups for long-range transport. In any case, a simple consideration of the steric volume of SOs groups in relation to the size of these channels leads to the conclusion that more than one group would have difficulty fitting into this very small volume. Related... 

The main difference between the two mechanisms as they relate to crystal size (discussed in Sec. 2.6) is that the cluster mechanism is three dimensional while the ion-by-ion one is mainly two dimensional. Crystal size in the former is limited largely by the amount of reactant per nucleus The more nuclei, the smaller the final crystal size, since the same concentration of reactants is divided over more nuclei. Temperature affects this by stabilizing (kinetically) smaller nuclei as temperature is lowered, thus increasing the number of nuclei at lower temperature. 

Ionic radii in the figure are measured by X-ray diffraction of ions in crystals. Hydrated radii are estimated from diffusion coefficients of ions in solution and from the mobilities of aqueous ions in an electric field.3-4 Smaller, more highly charged ions bind more water molecules and behave as larger species in solution. The activity of aqueous ions, which we study in this chapter, is related to the size of the hydrated species. 

It is of interest to compare the porphyrin and corrin macrocycles, and to consider the reactivities of porphyrin- and corrin-bound metal ions. These may be related to the size of the cavity. The corrin macrocycle provides a smaller cavity, into which cobalt fits tightly in the B12 coenzymes. Thus the cobalt does not move relative to the corrin plane, and remains coplanar with the four nitrogen donor atoms. The cobalt remains low-spin, and reactivity is controlled by the loss of the axial ligands, giving five- and four-coordinate species. 

In the case of anthracene, which forms large anions with delocalized charge, the ion-pairing effect is related to the size of the solvated cation the interaction increases as the solvated cation becomes smaller. 

Eliad L, Poliak E, Levy N, Salitra G, Soffer A, Aurbach D. Assessing optimal pore-to-ion size relations in the design of porous poly(vinylidene chloride) carbons for EDL capacitors. Applied Physics A 2006 82 607-613. 

We have fitted the viscosity of ionic liquids using hole theory [123]. The theory was developed for molten salts but has been shown to be very useful for ionic liquids. It was shown that the value of En is related to the size of the ions and the size of the voids present in the liquid [103]. The viscosity of ionic liquids is... 

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