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.