Expanded Shells and Molecular Orbitals

There are many books describing bonding and molecular orbitals, with levels ranging from those even more descriptive and qualitative than the treatment in this chapter to those designed for the theoretician interested in the latest methods. A classic that starts at the level of this chapter and includes many more details is R. McWeeny s revision of Coulson s Valence, 3rd ed., Oxford University Press, Oxford, 1979. A different approach that uses the concept of generator orbitals is that of J. G. Verkade, in A Pictorial 

5-2 Compare the bonding in 2, 02, and O2. Include Lewis structures, molecular orbital structures, bond lengths, and bond strengths in your discussion. 

5-3 Although the peroxide ion, 02, and the acetylide ion, C2, have long been known, the diazenide ion (N2 ) has only recently been prepared. By comparison with the other diatomic species, predict the bond order, bond distance, and number of unpaired electrons for N2. (Reference G. Auffermann, Y. Prots, and R. Kniep, Angew. Chem., Int. Ed., 2001, 40, 547) 

Prepare a molecular orbital energy level diagram for SH , including sketches of the orbital shapes and the number of electrons in each of the oibitals. If a program for calculating molecular orbitals is available, use it to confirm your predictions or to explain why they differ. 

Methylene, CH2, plays an important role in many reactions. One possible structure of methylene is linear. 

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