By the current definition, the lattice energy is always exothermic; the value of " ?H " is always negative, because it corresponds to the coalescing of ions, not the separation of ions.
32.
For a simple lattice consisting ions with equal and opposite charge in a 1 : 1 ratio, interactions between one ion and all other lattice ions need to be summed to calculate E _ M, sometimes called the Madelung or lattice energy:
33.
In general, a large counter cation or anion ( such as Cs +, [ SbF 6 ] " ) can help stabilize the polyhalogen ions formed in the solid state from lattice energy considerations, as the packing efficiency was increased.
34.
This occurs with the nickel ion Ni 2 + and dimethylglyoxime, ( dmgH 2 ) : in this case the lattice energy of the solid is not particularly large, but it greatly exceeds the energy of solvation of the molecule Ni ( dmgH ) 2.
35.
In general, beryllium has a tendency to bond covalently, much more so than the other lattice energy of the fluorite structure . ) However, BeF 2 has much lower electrical conductivity when in solution or when molten than would be expected if it were fully ionic.
36.
The antisymmetric exchange is of importance for the understanding of magnetism induced electric polarization in a recently discovered class of multiferroics : Here, small shifts of the ligand ions can be induced by magnetic ordering, because the systems tends to enhance the magnetic interaction energy on the cost of lattice energy.
37.
Beryllium difluoride is very soluble in water, unlike the other alkaline earths . ( Although they are strongly ionic, they do not dissolve because of the especially strong lattice energy of the fluorite structure . ) However, BeF 2 has much lower electrical conductivity when in solution or when molten than would be expected if it were fully ionic.
38.
Where " U " is the internal lattice energy, " E ZP " is the vibrational zero-point energy of the lattice, " T " is the absolute temperature, " V " is the volume and " S " is the entropy due to the vibrational degrees of freedom.
39.
Unlike hydrogen fluoride, anhydrous liquid hydrogen bromide is difficult to work with as a solvent, because its boiling point is low, it has a small liquid range, its dielectric constant is low and it does not dissociate appreciably into H 2 Br + and ions the latter, in any case, are much less stable than the bifluoride ions ( ) due to the very weak hydrogen bonding between hydrogen and bromine, though its salts with very large and weakly polarising cations such as lattice energies such as tetraalkylammonium halides.
40.
Unlike hydrogen fluoride, anhydrous liquid hydrogen iodide is difficult to work with as a solvent, because its boiling point is low, it has a small liquid range, its dielectric constant is low and it does not dissociate appreciably into H 2 I + and ions the latter, in any case, are much less stable than the bifluoride ions ( ) due to the very weak hydrogen bonding between hydrogen and iodine, though its salts with very large and weakly polarising cations such as lattice energies such as tetraalkylammonium halides.
