1. Lewis Dot Structures Gilbert Lewis
One of Americas most influential Chemist.

2. Lewis Dot Structures Gilbert Lewis
One of Americas most influential Chemist.

3. He was the first person to speak of electrons being shared rather then transferred. His was the first description of covalent bonding.

4. Lewis dot structures help us to understand the shape and structure of atoms. Bonds represent a pair of shared electrons while excess electrons are shown in lone pairs

5. Step 1
Identify what element are in the formula and how many valence electrons each one contributes to bonding.

6. Step 1
Identify what element are in the formula and how many valence electrons each one contributes to bonding.
H2O

7. Step 1
Identify what element are in the formula and how many valence electrons each one contributes to bonding.
H2O
H = 1v.e. x 2 =
O = 6v.e. x 1 =
Total v.e. available 8

8. The lowest electronegative atom tends to be the central atom.
Step 2
Identify the central atom. Most formulas are written with the central atom first.
The lowest electronegative atom tends to be the central atom.
H is never the central atom.

9. Step 2
Identify the central atom. Most formulas are written with the central atom first. The lowest electronegative atom tends to be the central atom. H is not ever the central atom.
H2O

10. H2O H O H Step 2 Central atom
Identify the central atom. Most formulas are written with the central atom first. The lowest electronegative atom tends to be the central atom. H is not ever the central atom.
H2O H O H
Central atom

11. Step 3
Draw a single line between the atoms which signify two shared electrons. Each bond removes two v.e. from the amount you started with.

12. Step 3
Draw a single line between the atoms which signify two shared electrons. Each bond removes two v.e. from the amount you started with.
Total v.e. 8 H O H

13. .. .. H O H H O H Step 3 Total v.e. 8 -4 4 remain or
Draw a single line between the atoms which signify two shared electrons. Each bond removes two v.e. from the amount you started with.
Total v.e. 8 -4 4
remain H O H or .. .. H O H

14. Step 4
Count and see how many electrons you still need to fulfill the octet rule for each element. Compare this number to how many electrons you have available.

15. H O H Step 4 Total v.e. 8 4 remain H has 2 and only needs 2 It’s good!
Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.
Total v.e. 8 4
remain H O H
H has 2 and only needs 2
It’s good!

16. H O H Step 4 Total v.e. 8 4 remain 2 H has 2 and only needs 2
Count and see how many electrons you still need to fulfill the octet rule for each element. Compare this number to how many electrons you have available.
Total v.e. 8 4
remain H O H 2
H has 2 and only needs 2
It’s good!

17. O has 4 and needs 8 so it needs 4 more
Step 4
Count and see how many electrons you still need to fulfill the octet rule for each element. Compare this number to how many electrons you have available.
Total v.e. 8 4
remain H O H 2 2
O has 4 and needs 8 so it needs 4 more

18. *If you have too many electrons place them on the central atom.
Step 5
*If you have enough electrons left just add them to each element in electron lone pairs.
*If you don’t have enough electrons you must share more electrons by forming additional bonds.
*If you have too many electrons place them on the central atom.

19. .. .. H O H Step 5 Total v.e. 4 -4 remain
*If you have enough electrons left just add them to each element in electron lone pairs. ..
Total v.e. 4 -4
remain H O .. H
Both H’s have 2 and O has 8 they all have full octets with no left over electrons.

20. Step 1
Identify what element are in the formula and how many valence electrons each one contributes to bonding.
CO2

21. Step 1
Identify what element are in the formula and how many valence electrons each one contributes to bonding.
CO2
C = 4v.e. x 1 =
O = 6v.e. x 2 =
Total v.e. available 16

22. Step 2
Identify the central atom. Most formulas are written with the central atom first. The lowest electronegative atom tends to be the central atom. H is not ever the central atom.
CO2

23. CO2 O C O Step 2 Central atom
Identify the central atom. Most formulas are written with the central atom first. The lowest electronegative atom tends to be the central atom. H is not ever the central atom.
CO2 O C O
Central atom

24. Step 3
Draw a single line between the atoms which signify two shared electrons. Each bond removes two v.e. from the amount you started with.
Total v.e. 16 O C O

25. .. .. O C O O C O Step 3 Total v.e. 16 -4 12 remain or
Draw a single line between the atoms which signify two shared electrons. Each bond removes two v.e. from the amount you started with.
Total v.e. 16 -4 12
remain O C O or .. .. O C O

26. O C O Step 4 Total v.e. 16 12 remain O has 2 and needs 6 more
Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.
Total v.e. 16 12
remain O C O
O has 2 and needs 6 more

27. O C O Step 4 Total v.e. 16 12 remain 2 O has 2 and needs 6 more
Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.
Total v.e. 16 12
remain O C O 2
O has 2 and needs 6 more

28. O C O Step 4 Total v.e. 16 12 remain 2 2 C has 4 and needs 4 more
Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.
Total v.e. 16 12
remain O C O 2 2
C has 4 and needs 4 more

29. *If you have too many electrons place them on the central atom.
Step 5
*If you have enough electrons left just add them to each element in electron lone pairs.
*If you don’t have enough electrons you must share more electrons by forming additional bonds.
*If you have too many electrons place them on the central atom.

30. O C O Step 5 Total v.e. 16 12 remain 2 4 2 Needs 6 Needs 4 Needs 6
Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.
Total v.e. 16 12
remain O C O 2 4 2
Needs 6
Needs 4
Needs 6
You have 12 electrons left but you still need 16. You don’t have enough and must add more bonds.

31. O C O Step 5 Total v.e. 16, 12 10 remain 4 6 2 Needs 4 Needs 2 Needs 6
Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.
Total v.e.
16, 12 10
remain O C O 4 6 2
Needs 4
Needs 2
Needs 6
You have 10 electrons left but you still need 12. You don’t have enough and must add more bonds.

32. O C O Step 5 Total v.e. 16, 12, 10 8 remain 4 8 4 Needs 4 Needs 0
Count and see how many electrons you still need to fulfill the octet rule. Compare this number to how many electrons you have available.
Total v.e.
16, 12, 10 8
remain O C O 4 8 4
Needs 4
Needs 0
Needs 4
You have 8 electrons left and you need 8. You have enough and do not need to add more bonds.

33. *If you have too many electrons place them on the central atom.
Step 5
*If you have enough electrons left just add them to each element in electron lone pairs.
*If you don’t have enough electrons you must share more electrons by forming additional bonds.
*If you have too many electrons place them on the central atom.

34. .. .. .. .. O C O Step 5 Total v.e. 8 -8 remain
*If you have enough electrons left just add them to each element in electron lone pairs. .. ..
Total v.e. 8 -8
remain O .. C O ..
All three atoms have 8 electrons and have full octets with no left over electrons.

35. Hints
*Always make sure the outside atoms have full octets. Place any odd electrons situations on the central atom.
*If you have a polyatomic cation subtract the positive charge from the starting # of valence electrons.
*If you have a polyatomic anion add the negative charge to the starting # of valence electrons