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Homework Problems Chapter 3

  • Page ID
    289734
  • Homework Problems

    Section 1

    Exercise 1

    What will lead most likely to the smallest covalent interaction:

    a) Overlap of a small and a large orbital.

    b) Overlap of two small orbitals.

    c) Overlap of two large orbitals.

    Answer

    a) Overlap of a small and a large orbital.

    Exercise 2

    What will lead most likely lead to the largest covalent interaction:

    a) orbital overlap in sigma-fashion

    b) orbital overlap in pi-fashion

    c) orbital overlap in delta fashion

    Answer

    a) orbital overlap in sigma-fashion

    Exercise 3

    Qualitatively construct the MO diagrams composed of

    a) two 2s atom orbitals A and B of equal energy.

    b) The orbital energy of atom A is significantly higher than that of B. Assuming both the bonding and the antibonding MO are filled with electrons: Where will bonding and antibonding electrons primarily be located. Explain briefly your decision.

    Answer

    clipboard_e3cee4985df573c08b0d6c550aaf03b94.png

    Exercise 4

    Decide by “inspection” which of the following combinations of orbitals have the “right” symmetries to form molecular orbitals.

    a) The 2px orbital of the first N atom and the 2py orbital of the second atom in the molecule N2. The z axis is defined as the bond axis in N2.

    b) The 2px (of F) and the 1s orbital (of H) in the HF molecule. The z axis is defined as the bond axis.

    c) The 2pz orbital of F and the 1s orbital in the HF molecule: The z axis is defined as the bond axis.

    Answer

    a) clipboard_e8cf2e54930f2ffa8c5e7f002e7be8148.png

    b) clipboard_e309f4f6258633e27dc17b81885977360.png

    c) clipboard_ed5d12884a06eac4671dca6e89ff10332.png

    Exercise 5

    The CH4 molecule belongs to the point group Td. You can find the character table of the point group in the internet.

    a) Calculate the reducible representation for the ligand group orbitals (LGOs).

    b) Calculate the irreducible representations of the ligand group orbitals (LGOs).

    c) Draw a qualitative molecular orbital diagram for CH4.

    Answer

    clipboard_e5e0391ad682044145c6b821ff6ea3dc5.png

    Exercise 6

    Which are the symmetry types of the central atom orbitals in the PCl5 molecule?

    Answer
    1. Determine point group of PCl5. --> D3h.
    2. Decide what are the valence orbitals of the central atom: 3s, 3p
    3. Look up the character table of D3h, eg. in the internet. You will find their symmetries to be: A1' (3s), A2'' (3pz), E'(3px, 3py)

    Exercise 7

    For the hypothetical BrKr+ molecule: Toward which atom is the HOMO polarized? Explain briefly why.

    Answer

    clipboard_ecae1b1aa43a36fec85848ef5fa1c494d.png

    clipboard_ec6ca5f5c0d7b7ab77743a2602cc39152.png

    Exercise 8

    Reconstruct the MO diagram for water and NH3 (repeat what we did in class without looking at your notes (only use the respective character tables).

    Answer

    Water

    clipboard_e26dc4d918791a61b2f2bfb390ff2a7a5.png

    NH3

    clipboard_e976881ff82a660ef1a5a42bdf75b11ab.png


    Dr. Kai Landskron (Lehigh University). If you like this textbook, please consider to make a donation to support the author's research at Lehigh University: Click Here to Donate.

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