Molecular symmetry - Symmetry adapted linear combinations
3 important questions on Molecular symmetry - Symmetry adapted linear combinations
What is the principle of the MO theory of diatomic molecules?
Molecular orbitals are constructed from atomic orbitals of the same symmetry.
Identify the symmetry species of the SALCs that may be constructed from the H1s orbital of NH3
An NH3 molecule has symmetry C3v and the three H1s orbitals all remain unchanged under the identity operation E. None of the H1s orbitals remain unchanged under a C3 rotation, and only one remains unchanged under a vertical reflection sigmav. E:3, 2c3:0 3sigmav:1. Reduce set of characters and see that it corresponds with A1+E --> three H1s orbitals contribute two SALCs, one with A1 and one with E symmetry.
What is the general procedure for constructing a molecular orbital scheme for a molecule
1. Assign a point group to the molecule
2. Look up the shapes of the SALCs in resource section 5
3. Arrange the SALCs of each molecular fragment in increasing order of energy, first nothing whether they stem from s,p, or d orbitals. And then their number of internuclear nodes
4. Combine SALCs of the symmetry type from the two fragments and from N SALCs from N molecular orbitals
5. Estimate the relative energies of the MO from consideration of overlap and relative energies of the parent orbital and draw the levels on a MO energy-level diagram
2. Look up the shapes of the SALCs in resource section 5
3. Arrange the SALCs of each molecular fragment in increasing order of energy, first nothing whether they stem from s,p, or d orbitals. And then their number of internuclear nodes
4. Combine SALCs of the symmetry type from the two fragments and from N SALCs from N molecular orbitals
5. Estimate the relative energies of the MO from consideration of overlap and relative energies of the parent orbital and draw the levels on a MO energy-level diagram
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