COVALENT
BONDING
Science 9
Rosalie R. Roxas
H
••
O
••
H
••
O
••
A single bond represents a pair of shared electrons.
How to draw Lewis Structures of Molecules.
1. Add up the number of valence electrons for each of the
atoms in the molecule.
2. Draw a trial structure. The trial structure has single bonds
connecting the atoms in your molecule.
3. Subtract the number of electrons in your trial structure from the
number of electrons in step 1. These are the electrons that need to be in
your trial structure but are not. It is possible to have this step be equal
to zero.
4. Take the electrons from step 3 and put this on your trial
structure. Your goal is to give every atom (except hydrogen) an
octet. Don’t put down more electrons than you are allowed.
5. If you cannot give every atom an octet in step 4, then
rearrange the electrons that you have to form double or triple
bonds. This step is the last resort.
How to draw Lewis Structures of Molecules.
Draw the Lewis Structure of the following:
a. H2O
b. HCl
c. CCl 4
d. CO 2 e. N2
1. Add up the number of valence electrons for each of the atoms
in the molecule.
H 2O
2 atoms H x 1 valence e = 2 v. e.
1 atom O x 6 valence e = 6 v. e.
8 v. e.
H•
H•
••
• O ••
•
How to draw Lewis Structures of Molecules.
2. Draw a trial structure. The trial structure has single bonds
connecting the atoms in your molecule.
H
O
H
How to draw Lewis Structures of Molecules.
3. Subtract the number of electrons in your trial structure from the
number of electrons in step 1. These are the electrons that need to be
in your trial structure but are not. It is possible to have this step be
equal to zero.
H
O
H
2 atoms H x 1 valence e = 2 v. e.
1 atom O x 6 valence e = 6 v. e.
8 v. e.
8 v. e. – 4 v. e. = 4 v.e.
How to draw Lewis Structures of Molecules.
4. Take the electrons from step 3 and put this on your trial
structure. Your goal is to give every atom (except hydrogen) an
octet. Don’t put down more electrons than you are allowed.
8 v.e. – 4 v. e. = 4 v.e.
H
••
O
••
H
How to draw Lewis Structures of Molecules.
HCl
1. Add up the number of valence electrons for each of the atoms
in the molecule.
1 atom H x 1 valence e = 1 v. e.
1 atom Cl x 7 valence e = 7 v. e.
8 v. e.
••
H • • Cl ••
••
How to draw Lewis Structures of Molecules.
2. Draw a trial structure. The trial structure has single bonds
connecting the atoms in your molecule.
HCl
H
Cl
How to draw Lewis Structures of Molecules.
3. Subtract the number of electrons in your trial structure from
the number of electrons in step 1. These are the electrons that
need to be in your trial structure but are not. It is possible to
have this step be equal to zero.
H
Cl
1 atom H x 1 valence e = 1 v. e.
1 atom Cl x 7 valence e = 7 v. e.
8 v. e.
8 v. e. – 2 v. e. = 6 v.e.
How to draw Lewis Structures of Molecules.
4. Take the electrons from step 3 and put this on your trial structure.
Your goal is to give every atom (except hydrogen) an octet. Don’t put
down more electrons than you are allowed.
H
••
Cl
••
•
•
1 atom H x 1 valence e = 1 v. e.
1 atom Cl x 7 valence e = 7 v. e.
8 v. e.
8 v. e. – 2 v. e. = 6 v.e.
How to draw Lewis Structures of Molecules.
CCl4
1. Add up the number of valence electrons for each of the atoms
in the molecule.
1 atom C x 4 valence e = 4 v. e.
4 atoms Cl x 7 valence e = 28 v. e.
32 v. e.
How to draw Lewis Structures of Molecules.
2. Draw a trial structure. The trial structure has single bonds
connecting the atoms in your molecule.
Cl
Cl
C
Cl
Cl
How to draw Lewis Structures of Molecules.
3. Subtract the number of electrons in your trial structure from the number
of electrons in step 1. These are the electrons that need to be in your trial
structure but are not. It is possible to have this step be equal to zero.
HCl
Cl
Cl
C
Cl
1 atom C x 4 valence e = 4 v. e.
4 atoms Cl x 7 valence e = 28 v. e.
32 v. e.
Cl
32 v.e.-8 v.e. = 24 v.e.
How to draw Lewis Structures of Molecules.
4. Take the electrons from step 3 and put this on your trial structure.
Your goal is to give every atom (except hydrogen) an octet. Don’t put
down more electrons than you are allowed.
••
•• Cl ••
•
•
••
Cl
••
C
• Cl •
• •
••
••
Cl ••
••
How to draw Lewis Structures of Molecules.
CO2
1. Add up the number of valence electrons for each of the atoms
in the molecule.
1 atom C x 4 valence e = 4 v. e.
2 atoms O x 6 valence e = 12 v. e.
16 v. e.
How to draw Lewis Structures of Molecules.
2. Draw a trial structure. The trial structure has single bonds
connecting the atoms in your molecule.
CO2
O
C
O
How to draw Lewis Structures of Molecules.
CO2
3. Subtract the number of electrons in your trial structure from
the number of electrons in step 1. These are the electrons that
need to be in your trial structure but are not. It is possible to
have this step be equal to zero.
1 atom C x 4 valence e = 4 v. e.
2 atom O x 6 valence e = 12 v. e.
16 v. e.
O
C
O
16 v. e. – 4 v.e. = 12 v. e.
How to draw Lewis Structures of Molecules.
4. Take the electrons from step 3 and put this on your trial
structure. Your goal is to give every atom (except hydrogen) an
octet. Don’t put down more electrons than you are allowed.
CO2
••
•• O
••
C
••
•
O•
••
16 v. e. – 4 v.e. = 12 v. e.
How to draw Lewis Structures of Molecules.
5. If you cannot give every atom an octet in step 4, then
rearrange the electrons that you have to form double or triple
bonds. This step is the last resort.
1 atom C x 4 valence e = 4 v. e.
2 atom O x 6 valence e = 12 v. e.
16 v. e.
CO2
••
•
•
O
••
•O
•
••
C
C
••
••
O
••
••
•
O•
••
16 v. e. – 4 v.e. = 12 v. e.
•O
•
••
C
•
O•
••
How to draw Lewis Structures of Molecules.
N2
1. Add up the number of valence electrons for each of the atoms
in the molecule.
2 atoms N x 5 valence e = 10 v. e.
How to draw Lewis Structures of Molecules.
2. Draw a trial structure. The trial structure has single bonds
connecting the atoms in your molecule.
N
N
How to draw Lewis Structures of Molecules.
3. Subtract the number of electrons in your trial structure from
the number of electrons in step 1. These are the electrons that
need to be in your trial structure but are not. It is possible to
have this step be equal to zero.
2 atoms N x 5 valence e = 10 v. e.
N
N
10 v. e. – 2 v. e. = 8 v.e.
How to draw Lewis Structures of Molecules.
4. Take the electrons from step 3 and put this on your trial structure.
Your goal is to give every atom (except hydrogen) an octet. Don’t put
down more electrons than you are allowed.
••
•N
•
••
•
N•
2 atoms N x 5 valence e = 10 v. e.
10 v. e. – 2 v. e. = 8 v.e.
How to draw Lewis Structures of Molecules.
4. Take the electrons from step 3 and put this on your trial structure.
Your goal is to give every atom (except hydrogen) an octet. Don’t put
down more electrons than you are allowed.
••
•• N
••
•N
•
•• N
••
•
N•
••
•
N•
••
•
N•
2 atoms N x 5 valence e = 10 v. e.
10 v. e. – 2 v. e. = 8 v.e.
•N
•
••
•
N•
•• N
••
N