Molecular structure complicated covalent 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. 

The nomenclature for molecular compounds is much less complicated than for ionic compounds. Molecular compounds are formed from covalently bonded nonmetallic elements. The formula for a molecule represents a stable unit of atoms, unlike a formula for an ionic compound, which only represents the simplest whole number ratio of ions. As a result, molecular formulas cannot be simplified like formulas for ionic compounds. An example would be hydrogen peroxide, H O. Although the formula could be reduced to HO, this would be inappropriate because 11,0, is a molecule. Changing the structure to HO would change the chemical composition. 

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