1. H-C-H: Carbon has 4 valence electrons, each hydrogen has 1. Total valence electrons = 4 + 3(1) = 7. But CH₃ is a methyl radical with an unpaired electron on carbon. The structure shown is incomplete; it should show 3 bonds to H and one unpaired electron on C.
2. H-N-H: Nitrogen has 5 valence electrons, each hydrogen has 1. Total = 5 + 3(1) = 8. Structure should have 3 single bonds to H and one lone pair on N (ammonia NH₃).
3. :O-H: Oxygen has 6 valence electrons, hydrogen has 1. Total = 7. This represents the hydroxyl radical. Structure should show O bonded to H with 3 lone pairs on O and one unpaired electron (total 7 electrons).
4. :F-F: Each fluorine has 7 valence electrons. Total = 14. Structure should show a single bond between F atoms and 3 lone pairs on each F.
5. :N-O: Nitrogen has 5, oxygen has 6. Total = 11. This is the nitrosyl radical. Structure should show a double bond between N and O, with 2 lone pairs on O and 1 lone pair plus 1 unpaired electron on N.
6. :S-: Sulfur has 6 valence electrons. With a negative charge, total = 7. Structure should show sulfur with 3 lone pairs and 1 unpaired electron (sulfide radical anion).
7. :P-: Phosphorus has 5 valence electrons. With a negative charge, total = 6. Structure should show phosphorus with 3 lone pairs (phosphide ion P³⁻ would have 8 electrons, but this notation suggests a radical anion with 6 electrons — likely a typo or misrepresentation).
8. :Cl-Cl: Each chlorine has 7 valence electrons. Total = 14. Structure should show a single bond between Cl atoms and 3 lone pairs on each Cl.
9. :O=O: Each oxygen has 6 valence electrons. Total = 12. Structure should show a double bond between O atoms and 2 lone pairs on each O (oxygen molecule O₂, which actually has two unpaired electrons — the Lewis structure shown is a simplified version).
10. :N=N: Each nitrogen has 5 valence electrons. Total = 10. Structure should show a double bond between N atoms and 2 lone pairs on each N (dinitrogen N₂ actually has a triple bond — this is incorrect).
11. H-C≡: Carbon has 4 valence electrons, hydrogen has 1. Total = 5. This represents the ethynyl radical. Structure should show C bonded to H with a triple bond to another atom (not shown), and one unpaired electron on C.
12. H-C≡N: Carbon has 4, hydrogen has 1, nitrogen has 5. Total = 10. Structure should show H-C triple bond N, with a lone pair on N (hydrogen cyanide).
13. :C::: This notation is unclear. If meant to be :C: (carbene), carbon has 4 valence electrons. Structure should show C with 2 lone pairs and 2 unpaired electrons (or one lone pair and two single bonds). If meant to be :C: with two dots, it’s carbene with 2 lone pairs.
14. :O=C=O: Carbon has 4, each oxygen has 6. Total = 16. Structure should show O=C=O with 2 lone pairs on each O (carbon dioxide).
Parent Tip: Review the logic above to help your child master the concept of lewis structure worksheet.
