A covalent bond represents the sharing of an electron pair between atoms. By sharing electrons, as we first described it in Properties of Bonds, each atom in a bond can achieve stability by having an octet of valence electrons. To keep track of the electrons surrounding each atom in a covalent bond, we will introduce Lewis structures. When drawing Lewis structures we will learn how to calculate the charges on individual atoms in molecules by using the concept of formal charge.
Often, when drawing Lewis structures we forget that molecules are real things with three dimensional shapes. To describe the shapes of molecules we will use Valence Shell Electron Pair Repulsion theory (VSEPR). As we know from Coulomb's law (in the SparkNote on ionic bonding), electrons repel each other. VSEPR simply states that the most stable shape for a molecule will be the one that places the electrons farthest apart. In this section, we will fully explore the consequences of VSEPR for the shapes of the common types of molecules you will encounter.