Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.
- Develop a deeper understanding and appreciation of MO theory
- Be able to construct a MO diagram for BN
- Be able to apply MO theory to explain observed phenomenon
Hexagonal Boron nitride and graphite are isostructural and isoelectronic. Band gap theory can be used to determine if graphite was an insulator or a conductor. Let’s use the same theory and logic to develop the same information about boron nitride.
- Draw the structure for Boron nitride that you would expect from the information given, isostructural and isoelectronic with graphite and the rings are made of 3 B’s and 3 N’s.
- Do you think it is best to treat h-BN as a molecular crystal or as an atomic crystal?
- If you use the method of molecular crystal, what would be the simplest molecular model we could use?
- What central atom will you choose? What is the hybridization around the central atom in the model chosen in #2?
- Construct the MO diagram for hexagonal BN, start with the central atom you chose in #3, then hybridize as needed, then fill in the model for the simplest molecular model and then create the bands that occur when N=1023.
- Is h-BN an insulator or a conductor? Explain why you chose your answer.
- Is h-BN white or black? Explain why you choose your answer.
- Kelley J. Donaghy, SUNY-ESF