Orbital energy diagram

You can order the molecular orbitals that are a solution to equation (47) according to their energy. Electrons populate the orbitals, with the lowest energy orbitals first. Anormal, closed-shell, Restricted Hartree Fock (RHF) description has a maximum of two electrons in each molecular orbital, one with electron spin up and one with electron spin down, as shown  

If the number of electrons, N, is even, you can have a closed shell (as shown) where the occupied orbitals each contain two electrons. For an odd number of electrons, at least one orbital must be singly occupied. In the example, three orbitals are occupied by electrons and two orbitals are unoccupied. The highest occupied molecular orbital (HOMO) is /3, and the lowest unoccupied molecular orbital (LUMO) is 11/4. The example above is a singlet, a state of total spin S=0. Exciting one electron from the HOMO to the LUMO orbital would give one of the following excited states  

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Determine the symmetries of the resultant moleeular orbitals in the D3h point group. Draw a qualitative orbital energy diagram using the HMO energies you have ealeulated. 

Use Frosts circle to construct orbital energy diagrams for (a) [lOjannulene and (b) [12]annulene Is either aromatic according to Huckel s rule ... 

You will need to decide whether or not to request Restricted (RHF) or Unrestricted (UHF) Hartree-Fock calculations. This question embodies a certain amount of controversy and there is no simple answer. The answer often depends simply on which you prefer or what set of scientific prejudices you have. Ask yourself whether you prefer orbital energy diagrams with one or two electrons per orbital. 

Fig. 1.18. Molecular orbital energy diagram for methane. Energies are in atomic units. ...

Use Frost s circle to construct orbital energy diagrams for (a)... 

Figure 17.2 Schematic molecular orbital energy diagram for diatomic halogen molecules. (For F2 the order of the upper and 7T bonding MOs is inverted.).

Figure 6.6 shows the molecular orbital energy diagrams for a few homonudear diatomic molecules. The stability of the molecules can be estimated from the number of electrons occupying bonding orbitals compared with the number of electrons in the antibonding orbitals. (Antibonding orbitals are sometimes denoted with the subscript, as in 2jt. )... 

Figure 3.7 shows both of the molecular orbital energy diagrams that result for diatomic molecules of second-row elements. 

These two 02+ ions have slightly different energies, as is exhibited by their photoelectron spectra. Studies such as these have contributed greatly to our understanding of molecular orbital energy diagrams. We will not describe the technique further, but more complete details of the method and its use can be found in the references at the end of this chapter. 

Figure 11. Stereochemistry and d-orbital energy diagram of the tetragonal Cu(H20)g2+ ion.

Use and interpret simple atomic and molecular orbital energy diagrams. 

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