In this section we will analyze the geometry of the molecules, using the valence shell electron pair repulsion theory VSEPR. This will allow us to know the spatial distribution of the atoms in the molecule, a fundamental issue to predict physical properties and reactivity of chemical compounds.

Secondly, we will develop the valence bond theory (VTE), which will help us understand how covalent bonds are formed between the atoms of a molecule. This theory uses the concept of hybridization to explain the experimental facts.

Finally, we will describe in great detail the theory of molecular orbitals (TOM), based on quantum mechanics, allows us to explain certain experimental data, impossible to explain with the TEV.