3.2 Molecular Orbitals
LEARNING GOALS
After Chapter 3.2, you will be able to:
Describe the stability and energy of bonding and antibonding orbitals
Explain how the addition of a double or triple bond affects the electron density and
molecular orbitals within a molecule
Order the different orbital types based on strength
When two atomic orbitals combine, they form molecular orbitals. Molecular orbitals are obtained
mathematically by adding or subtracting the wave functions of the atomic orbitals. While the
mathematics of combining wave functions is outside the scope of the MCAT, some questions may
ask for the visualization of molecular orbitals, as shown in Figure 3.2. If the signs of the wave
functions are the same, a lower-energy (more stable) bonding orbital is produced. If the signs are
different, a higher-energy (less stable) antibonding orbital is produced.