1. Lewis Dot Structure …for CH4
How to create a…
Lewis Dot Structure
…for CH4
#1 Count the total number of valence electrons in the molecule
C: 4 electrons x 1 atom = 4 valence electrons
H: 1 electron x 4 atoms = 4 valence electrons
Total = 8 valence electrons

2. Lewis Dot Structure …for CH4
How to create a…
Lewis Dot Structure
…for CH4
#2 Find the number of “octet” electrons for the molecule.
C: 8 octet electrons x 1 atom = 8 octet electrons
H: 2 octet electrons x 4 atoms = 8 octet electrons
Total = 16 octet electrons
Rules: Hydrogen always has 2 octet electrons
Beryllium always has 4 octet electrons
Boron wants 6 for neutral molecules (8 if it’s an anion)

3. Lewis Dot Structure …for CH4
How to create a…
Lewis Dot Structure
…for CH4
#3 Subtract the number of valence electrons from the number of octet electrons to find the number of bonding electrons.
16 – 8 = 8 bonding electrons

4. Because there are two electrons in every covalent bond!
How to create a…
Lewis Dot Structure
…for CH4
#4 Divide the number of bonding electrons by 2 to find the number of bonds in the molecule.
8 / 2 = 4 bonds in CH4
Why 2?
Because there are two electrons in every covalent bond!

5. Lewis Dot Structure …for CH4
How to create a…
Lewis Dot Structure
…for CH4
#5 Draw an arrangement of atoms that has the number of bonds you found in step 4. Of course, there are more rules…
Hydrogen and Halogens = bond once!
Oxygen’s family and Beryllium bond twice in neutral molecules
Nitrogen’s family and Boron bond 3 times in neutral molecules
Carbon’s family = bonds 4 times!

6. Lewis Dot Structure …for CH4 More hints… How to create a…
If you bond everything together and you have bonds left over, look for double/triple bonds.
The atom nearest to the left side of the periodic table is probably in the middle of the molecule.

7. Draw the Lewis structures for the following compounds:
H2O
CCl4
NH3   
CO2
PCL3

8. Draw the Lewis structures for the following compounds:
CH4
C2H6
CH3OH
BH3

9. Draw the Lewis structures for the following compounds:
PBr3
N2H2
  C2H2
SiH4
C2H4

10. Draw the Lewis structures for the following compounds:HF
  HCl
CCl2F2