Problem 1: Molecular orbitals and Valence Bond Theory: Why is O2 a paramagnetic species even though by VBT is should adopt a diamagnetic electronic structure? Use orbital diagrams or drawings to explain your answer.
Problem 2: Unusual Structures and VBT: Valence Bond Theory (VBT) is useful for predicting the structure and reactivity many simple molecules, but in many cases, it is an inaccurate description of bonding. Borane (BH3) actually exists as a dimer (B2H6) with the structure drawn below. The hydride is in an "unusual" bonding situation: the s orbital is bonding to two boron atoms. In the field of organ metallic chemistry, there are many examples of this type of bonding in other types of atoms, too.
a. What is the number of electrons for the whole molecules? Remember, the molecules is neutral, so the electron count must equal the total valance electrons of each atom.
b. What is the electron count per boron center?
c. If you were to naively multiply your answer from part (b) by 2 (because there are two Boron atoms), would your answer match the answer in part (a)?
d. According to VBT, what would the electron count be around the bridging H atom? Is that possible for an s hybridization?
e. What would the hybridization of H have to be according to VBT? What geometry is normally expected for this hybridization, and how does it compare to the actual geometry?
f. If your answers for (a)-(e) were correct, you would conclude that a VBT description of diborane is not very good. Since the Boron atoms do actually have an octet, how do you describe the B-H-B bonding? Please feel free to do research to answer the question.