Halides lattice energies, table

These trends are apparent In the values of lattice energy that appear in Table Notice, for example, that the lattice energies of the alkali metal chlorides decrease as the size of the cation increases, and the lattice energies of the sodium halides decrease as the size of the anion increases. Notice also that the lattice energy of MgO is almost four times the lattice energy of LiF. Finally, notice that the lattice energy of Fc2 O3, which contains five ions in its chemical formula, is four times as large as that of FeO, which contains only two ions in its chemical formula. 

The ligand field stabilization is expressed in the lattice energies of the halides MX2. The values obtained by the Born-Haber cycle from experimental data are plotted v.v. the d electron configuration in Fig. 9.5. The ligand field stabilization energy contribution is no more than 200 kJ mol-1, which is less than 8% of the total lattice energy. The ionic radii also show a similar dependence (Fig. 9.6 Table 6.4, p. 50). 

As was indicated in Sec. 1.2, the conclusion that the deformation phenomena play the smallest role in NaF was based first on the statement that its heat of sublimation (S) constitutes among the alkali halides the largest fraction of the lattice energy (17). The corresponding data in Table 5 show that the gradation of this fraction, SjU, is in fact closely parallel to that of the degree of polarity p both properties show a... 

TABLE 1.16 Lattice energies of some alkali and alkaline earth metal halides at 0 K... 

It is not yet possible to measure lattice energy directly, which is why the best experimental values for the alkali halides, as listed in Table 1.16, are derived from a thermochemical cycle. This in itself is not always easy for compounds other than the alkali halides because, as we noted before, not all of the data is necessarily available. Electron affinity values are known from experimental measurements for... 

TABLE 3.7. Heats of Formation and Lattice Energies of Alkali Metal Halides ... 

Table 5.2 Experimental and calculated (Kapustinskii equation) lattice energies of selected crystalline halides. All energies are in kJ mol ...

Table 4.2.4. Lattice energies (in kJ mol 1) of some alkali metal halides and divalent transition metal chalcogenides...

Table 4. Lattice enthalpies of the alkali halides at 298.2° K and 1 aim. from lattice energies computed by the Huggins-Mayer-type treatment (kcal mole-1)...

Many elements exhibit several different oxidation states, and the relative stabilities of MX and MX are often more difficult to assess. Assuming the lattice energy to be inversely proportional to the shortest M-X distance in the structure, then, since halide ion radii increase from F to I (Table 1), fluorides generally have the largest values and iodides the smallest values for lattice energies. However, one has to consider the stabilities of fluorides or iodides with respect to each other, for example, a solid salt MX +i decomposing into another, MX , and 1/2X2. From the Bom-Haber cycle (with some approximations) one obtains for such a reaction... 

Table 3. Energetic parameters of oxide and halide lattices relating to upconversion involving the I9/2 state of Er +, compiled from various literature sources. A (cm 0 is the average Er + " 19/2 energy gap, (cm ) is the highest-energy lattice phonon energy,p is the reduced energy gap, /c p is the estimated multiphonon-relaxation rate constant, is the estimated range of radiative rate constants, and /Ctot = Kad + /c p. Adapted from [26]...

Table CLI. Lattice Energies of Silver and Copper Halides...

For the constitution of the ionic lattices also, the Van der Waals attraction has been found to be a very decisive factor. We know the forces at present much better for these ions than for the neutral molecules. Using an interaction of the form (21), Born and Mayer have calculated the lattice energy of all alkali halides for the NaCl-type and simultaneously for the CsCl-type and comparing the stability of the two types they could show quantitatively that the relatively great Van der Waals attraction between the heavy ions Cs, I , Br, Cl cf. Table II.) accounts for the fact that CsCl, CsBr, Csl, and these only, prefer a lattice structure in which the ions of the same kind have smaller distances from each other than in the NaCl-type. The contribution of the Van der Waals forces to the total lattice energy of an ionic lattice is of course a relatively small one, it varies from I per cent, to 5 per cent., but just this little amount is quite sufficient to explain the transition from the NaCl-type to the CsCl-type. 

The monohalides of the coinage metals, with the exception of AgF, are almost insoluble in polar solvents. Copper(I) halides all have the zinc blende structure they show a predominantly covalent character in agreement with the observed lattice energies (p. 92) (Table 130). 

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