10. Why is diamond so hard, whereas graphite is soft, if both are only pure carbon?

11. Why does the percent ionic character of the bonds to the central atom increase in the series of molecules: methane, ammonia, water? What effect does this have on the measured dipole moment of each molecule?

12. Why would the methane molecule not have a measurable dipole moment, even if the individual C-H bonds were strongly polar?

13. How are conjugated molecules different from other molecules with double bonds? What is the term for conjugated ring compounds such as benzene?

14. Why does graphite conduct electricity, whereas diamond does not?