Molecular structure more complicated ionic compounds

In order to fully appreciate and understand molecular structure, you will need to be able to construct representations of various molecules. One of the easiest ways to do this is using Lewis structures. The procedure is a bit more complicated than for ionic compounds because of the increasing complexity of covalent compounds. The basic procedure for constructing Lewis diagrams of molecules consists of 4 steps ... 

Since the Braggs first determination, thousands of structures, most of them far more complicated than that of sodium chloride, have been determined by x-ray diffraction. For covalently bonded low molecular weight species (such as benzene, iodine, or stannic chloride), it is often of interest to see just how the discrete molecules are packed together in the crystalline state, but the crystal structures affect the chemistry of such substances only to a minor degree. However, for most predominantly ionic compounds, for metals, and for a large number of substances in which atoms are covalently bound into chains, sheets, or three dimensional networks, their chemistry is very largely determined by the structure of the solid. 

Alkali halides are compounds with a strong ionic character and without a solvent they are stabilized by the strong electrostatic interaction between the cation and the anion. In the present study we limit attention to the dissociation potentials comparing the curves obtained for the free molecule and for the molecule in water solution. The solvent is treated only as a continuum medium and then in this way we cannot consider the formation of complexes between the ions and the water molecules which instead are extensively studied by means of Monte Carlo (MC) and molecular dynamics (MD) simulations (see for example [13]). Although it could be possible to include some water molecules with the sodium chloride as a more complicated solute, we have preferred to focus attention on the solvent effect on the electronic structure of the simplest solute, this effect being the most important in the next two examples. 

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