It is very important to know the shape of a molecule if one is to understand its reactions. It is also desirable to have a simple method to predict the geometries of compounds. For main group compounds, the VSEPR method is such a predictive tool and unsurpassed as a handy predictive method. It is a remarkably simple device that utilizes a simple set of electron accounting rules in order to predict the shape of, in particular, main group compounds. Organic molecules are treated just as successfully as inorganic molecules.
Application of the VSEPR method requires some simplifying assumptions about the nature of the bonding. Despite this, the correct geometry is nearly always predicted, and the exceptions are often rather special cases. In a complete analysis of the geometry of a molecule it would be necessary to consider such factors as nuclear-nuclear interactions, nuclear-electron interactions, and electron-electron interactions.