1. Valence Bond Theory

2. What is it? Created by Linus Pauling – Go America! It is a good qualitative view of the bonding of atoms The main idea is…… Bonds are formed by overlap of orbitals The orbitals overlap at the best distance between the repulsive forces and attractive forces This is where they have the lowest potential energy

3. How is this different than the Molecular orbital theory (MO) molecular orbital theory is a more quantitative theory. It is said that molecular orbitals are spread out or delocalized over the molecule This is important for higher energy excited states and for molecules like NO or oxygen We will not be covering this theory

4. Let us look at the hydrogen bond using the valence bond theory The covalent bond is between two s orbitals. This is called a sigma bond (σ). The bond is formed by the overlap of orbitals head to head, with the electron density concentrated along the axis of the bond Orbitals overlap to form a bond between 2 atoms Two electrons, of opposite spin, are in overlapping orbitals. One electron is supplied by each atom The bonding electrons have a higher probability being found simultaneously attracted to both nuclei.

5. What about double bonds? These bonds overlap