1. Lewis Dot Structure Rules
Chemistry of Art:
Seurat employed a then-new pigment in his painting, a zinc chromate yellow that he hoped would properly capture the highlights of the park's green grasses. But for years this pigment has been undergoing a chemical reaction that began turning it brown even in Seurat's lifetime.
Georges-Pierre Seurat 
A Sunday on
La Grande Jatte—1884
1886 (French)

2. Arrange skeletal structure with least electronegative element in center (but not hydrogen!)
Determine the total valence electrons.
Add electrons to structure to make single bonds.
Add electrons to outer atoms to fill octets (exception: H, Be, B)

3. Add remaining electrons to central atom as lone pairs.
If necessary, move lone pairs from outer atoms to make multiple bonds to satisfy octet rule on central atom.
Place brackets and charge on polyatomic ions.
Check that octet rule is followed

4. Reminders!!!
H fills with only 2 electrons, Be with only 4 electrons, and B with only 6 electrons.
C,N,O,P, and S all can form double or triple bonds. (Remember “C-NOPS”)
Non-metals in periods 3-7 can have more than an octet due to presence of d-orbitals.

5. Example 1: H2CO
Step 1: H C O H

6. Example 1: H2CO
Step 2: = 12 H C O H

7. Example 1: H2CO
Step 3: H C O H

8. Example 1: H2CO
Step 4: H C O H

9. Step 5: Not necessary as there are no remaining valence electrons.
Example 1: H2CO
Step 5: Not necessary as there are no remaining valence electrons. H C O H

10. Example 1: H2CO
Step 6: H C O H

11. Example 1: H2CO
Step 7: Not necessary. H C O H

12. Step 8: Check that octet rule is fulfilled.
Example 1: H2CO
Step 8: Check that octet rule is fulfilled.
Yes! H C O
Yes!
Yes! (Only need 2 for hydrogen) H
Yes!

13. Example 1: H2CO
That’s it! H C O H

14. Let’s try a polyatomic ion
Example 2: PO43-
Let’s try a polyatomic ion

15. Example 2: PO43-
Step 1: O O P O O

16. Example 2: PO43-
Step 2: =32 O O P O O

17. Example 2: PO43-
Step 3: O O P O O

18. Example 2: PO43-
Step 4: O O P O O

19. Steps 5 and 6: Not necessary.
Example 2: PO43-
Steps 5 and 6: Not necessary. O O P O O

20. Example 2: PO43-
Step 7: 3- O O P O O

21. Example 2: PO43-
Step 8: 3- O O P O O