5. Two valence electrons, both unpaired.

6. Seven valence electrons, one unpaired.

7. The outer shell neon electron feels the greater force. There are fewer shielding inner electrons in neon.

9. P < Ge < Sn < Tl.

10. Pb < Sn < As < P.

12. One.

13. Na⁺ has zero electrons in the third shell. Cl^- has eight electrons in the third shell.

17. Group I elements all have a single unpaired valence electron which is removed (lost) much easier than electrons located in the next inner most shell. Group II elements each have 2 valence electrons which are removed (lost) much easier than electrons located in the next inner most shell.

20. Its outer most shell (the second) is full.

22. H, Br, C, neither.