| | Organic Chemistry at Penn State: Quantum Primer III (Site not responding. Last check: 2007-10-27) |
 | | All atoms in the molecule provide their atomic orbitals for construction of MO, but not all atomic orbitals must participate in all MO. The number of MO is equal to the number of atomic orbitals used to generate them. |
 | | The usual energy order of MO is as follows: σ-type orbitals (the lowest energy), π-type orbitals, n-type orbitals (nonbonding, such as lone pairs), π*-type orbitals and σ*-type orbitals (the highest in energy). |
 | | Since interaction between filled (occupied) orbitals does not result in net bonding (electron-electron repulsion), and interaction between empty (unoccupied) orbitals cannot contribute to bonding (no electrons to be shared) only the interaction between occupied and unoccupied will provide the initial impetus for the reorganization of existing bonding. |
| courses.chem.psu.edu /chem38/quantum/quantum3.html (1337 words) |