1. Energy, probability and electrons 2. An introduction to the dynamics of microsystems 3. One electron atoms: atomic orbitals 4. The one electron molecule H2+: molecular orbitals 5. Many electron atoms and the orbital concept 6. Orbitals in diatomic molecules 7. Orbitals in polyatomic molecules 8. Molecular orbitals and electron pair bonding 9. p Molecular orbitals: conjugation and resonance 10. Patterns in localised chemical bonds 11. The concept of molecular orbitals in other systems 12. Orbitals in action.