5. What second-row atoms can make double and triple electron-pair bonds? How do the bond lengths of single, double, and triple bonds between the same kinds of atoms compare? How might you expect the bond energies to vary?

6. What kinds of bonds are found between carbon atoms in benzene?

7. In what way is the benzene molecular structure like that of graphite?

8. What holds benzene molecules together in liquid benzene? What holds the carbon sheets together in a stack in graphite? How does this explain graphite's usefulness as a lubricant? In what way is this like the reason for the lubricant properties of hydrocarbons with 15 to 20 carbon atoms?

9. In what way is the structure of straight- and branched-chain hydrocarbons like that of diamond?