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The p-orbitals oriented in the z-direction (p z) can overlap end-on forming a bonding (symmetrical) σ orbital and an antibonding σ* molecular orbital. In contrast to the sigma 1s MO's, the σ 2p has some non-bonding electron density at either side of the nuclei and the σ* 2p has some electron density between the nuclei.
The qualitative approach of MO analysis uses a molecular orbital diagram to visualize bonding interactions in a molecule. In this type of diagram, the molecular orbitals are represented by horizontal lines; the higher a line the higher the energy of the orbital, and degenerate orbitals are placed on the same level with a space between them.
The molecular orbital diagram for the final state describes the electronic nature of the molecule in an excited state. Although in MO theory some molecular orbitals may hold electrons that are more localized between specific pairs of molecular atoms, other orbitals may hold electrons that are spread more uniformly over the molecule.
The orbital diagram breaks down as follows: The 18 framework molecular orbitals, (MOs), derived from the 18 boron atomic orbitals are: 1 bonding MO at the center of the cluster and 5 antibonding MOs from the 6 sp-radial hybrid orbitals; 6 bonding MOs and 6 antibonding MOs from the 12 tangential p-orbitals.
This lists the character tables for the more common molecular point groups used in the study of molecular symmetry. These tables are based on the group-theoretical treatment of the symmetry operations present in common molecules, and are useful in molecular spectroscopy and quantum chemistry. Information regarding the use of the tables, as well ...
Added orbital diagrams for molecular orbitals. 16:49, 21 May 2015: 2,020 × 1,070 (138 KB) Officer781: 2pz MO in wrong orientation relative to the other orbitals per the LCAO notation. 16:40, 21 May 2015: 2,020 × 1,070 (138 KB) Officer781: Moved 2s orbital higher in energy as that MO has more hydrogen admixture.
An initial assumption is that the number of molecular orbitals is equal to the number of atomic orbitals included in the linear expansion. In a sense, n atomic orbitals combine to form n molecular orbitals, which can be numbered i = 1 to n and which may not all be the same. The expression (linear expansion) for the i th molecular orbital would be:
Figure 5: Molecular orbital diagram depiction of frontier orbitals in methane and a basic ML 6 metal complex. As seen above, when a fragment is formed from CH 4, one of the sp 3 hybrid orbitals involved in bonding becomes a nonbonding singly occupied frontier orbital. The frontier orbital’s increased energy level is also shown in the figure.