Questions


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Molecular Orbitals in Inorganic Chemistry

Your questions answered

This page has become to long, and so I have split the questions into general questions which are answered here and then main group and TM questions which each have their own page:

More general questions


  1. Q: I am worried that I will lose marks in the exam, there are a lot of places to go wrong with MO diagrams!
    A: In the exam I am looking for evidence that you are making reasonable deductions and assumptions. Thus, the annotations are very important because they tell me you are thinking about where energy levels go and rationalising their position and interactions. This also means that if you place an energy level in the wrong place but then complete the diagram correctly and consistently with respect to a single simple mistake, you will likely get all the marks for the method and only loose one or two due to the mistake. I spread the marks out to cover all the components of the MO diagram, so even if you make a mistake, but you have the basic form of the diagram correct in all other respects, you can still get a high grade. Here is a typical mark allocation scheme:
    • 1 axial system defined in correct alignment
    • 1 fragments and molecule on diagram, placeholders present
    • 1 depicting and labelling FOs
    • 1 energy level placement FOs
    • 2 for shapes of MOs including size of FO contributions
    • 1 correct symmetry labels MOs
    • 2 MO energies roughly right
    • 1 correct electronic configuration
    • 3 for a selection of annotations related to MOs and energies
    • 1 discretionary
    A note here that easy annotations are worth 1/2 mark and more sophisticated annotations a whole mark. Repetition of the same annotation but applied to different MOs gets no extra marks. A simple annotation is "the energy of the antibonding MO is always destabilised more than the bonding MO is stabilised". A more complext annotation is "the size of the FO component is dependent on the relative energy of the FO, deeper energy FOs contribute more to the bonding MO"

  2. Q:
    A: