Covalent Bonding
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.
