7. Which of the gases among the second-shell elements are diatomic like , and which are monatomic like He?

8. What is the difference between the covalent radius and the nonbonded or packing radius of an atom?

9. What is "ionization" of an atom? How many electrons will an atom of lithium give up easily? How many will beryllium give up when it ionizes? How many will boron give up? What do these numbers tell us about electron-shell structure?

10. Why does carbon not ionize in its ordinary chemical reactions? If it did, what would be the charge on the ion, following the principle implied in the preceding question? What do carbon atoms do instead of ionizing?

11. Does a fluorine atom gain, or lose, electrons when it ionizes? Why? How many electrons are gained or lost when an oxygen atom forms an oxide ion? What neutral atom has the same number of electrons as these ions?