1. Drawing Lewis Structures
Example 1 - CCl4
Step 1 - Determine the total # of valence shell electrons (e1-) used.
C is in group 4, Cl is in group VII
((4x 1) + (7x4)) = 32 e1-
1 C atom in CCl4
4 Cl atoms in CCl4

2. Step 2 - Place the single atom of C in the centre and place the 4 Cl atoms around it.

3. Step 3- Place a pair of electrons between each pair of atoms.Cl

4. Step 4 - Place 8 electrons around all non-central atoms.Cl

5. Step 5 - If there are any electrons left, place them, in pairs, around the central atom .
Example - In the case of SI4 after going through steps you get:
Step3 I
Step 2
Step 5
Step 1
# of e1- is:
6 x x 7 = 34 S
Step4

6. Step 6 - If the central atom is in group 4, 5, 6, 7 or 8 the octet rule (rule of 8) must be satisfied by moving electron pairs from non-central atoms to central atoms, creating double bonds in the process. Example - SO2

7. S O S O Step 1 Step 2 & 3 # of e1- is: 6 x 1 + 6 x 2 = 18 Step 4

8. Draw Lewis Structures for the following:
SO2, CBr4, H2S, PBr5, SBr4, SeI2, SiS2, ClBr5, AlI3, SeS3,