1. Covalent Bonding & Lewis Structures
Octet Rule:
Atoms form bonds to obtain stable electron configurations…
8 e–’s in the outer shell like noble gases.

2. lone pair
nonbonded pair
unshared pair
1 shared pair
1 covalent bond
single bond:
1 pair of shared e–’s

3. How many unshared pairs?
structural formula:
shows the arrangement of atoms
How many unshared pairs? 2

4. How many shared pairs? 3

5. N N O O Super Special Carbon C double bond: 2 pairs of shared e–’s
triple bond:
3 pairs of shared e–’s
N N
Super Special Carbon C
Carbon can form long chains because it forms up to 4 bonds on each C atom.
This allows large biomolecules to form such as:
proteins
lipids (fats)
carbohydrates (sugars/starches)
nucleic acids (DNA/RNA)

6. Drawing Lewis Structures
In 5 easy steps:
PCl3
Count
Connect
Octet
(if necessary)

7. Drawing Lewis Structures
COUNT valence e–’s of all atoms in the molecule.
PCl3
(7) = 26

8. Drawing Lewis Structures
CONNECT atoms to the central atom with single bonds.
Central atom is the least electronegative (never H)
Keep track of the electrons:
26  6 = 20

9. Drawing Lewis Structures
OCTET
fill outer octets
Keep track of the electrons:
26  6 =  18 = 2

10. Drawing Lewis Structures
OCTET
fill central octet
Draw the Lewis structure for HCN
Keep track of the electrons:
26  6 =  18 = 2 2  2 = 0

11. Drawing Lewis Structures
If you run out of e–’s before the central atom has an octet…
…form multiple bonds until it does.

12. Drawing Lewis Structures
In 5 easy steps:
Count (val e–’s)
Connect (bonds)
Octet (outer dots)
Octet (central dots)
(if necessary)
form Multiple Bonds to fill central octet

13. O C O O C O Draw the Lewis structure for trichloromethane, CHCl3
Draw the Lewis structure for carbon dioxide, CO2
O C O
O C O

14. large, long chain biomolecules. nucleic acids carbohydrates
Quick Quiz!
1. Carbon atoms have 4 valence electrons to form up to 4 bonds. This allows carbon to form ______________ needed for life.
large, long chain biomolecules.
nucleic acids
carbohydrates
ALL of the above

15. Quick Quiz.
2. Which of the following diatomic molecules have a triple bond?
(hint: draw the Lewis structures) O2 N2
Br2 H2
O O
N N
Br Br
H H

16. Quick Quiz.
3. Draw the correct Lewis structure for dinitrogen monoxide , N2O (aka: nitrous or laughing gas)
hint: arrange the atoms as…
N N O
N N O