1. Covalent Bonding Lewis Structures

2. Bonding with Nonmetals
When no metal is present to donate electrons, nonmetals can share electrons to fill their valence shells. F F
Bond formation DECREASES total potential energy (energy lost), Bond Breakage INCREASES total potential energy (absorb energy)

3. Bonding with Nonmetals
Each atom donates an un-paired electron to be shared in the covalent bond. F F
circle new pair
Both atoms have access to this new pair of atoms some of the time.

4. Multiple Covalent Bonds
For atoms with more than one unpaired valence electron, multiple covalent bonds between the two atoms can form. S O
Two atoms can form single, double, or triple covalent bonds.

5. Multiple Covalent Bonds
Each bond represents a pair of electrons, one from each atom being bonded. H S N
More bonds will bring the atoms closer together and the bond will be stronger (more energy required to break it).
Strong bonds have low PE already, so more KE must be added to break them.

6. Lewis Structures
Lewis structures show the atom symbols, covalent bonds, and unbonded electrons for covalent molecules. Cl

7. Drawing Lewis Structures
1) Count the total number of valence electrons in all atoms in the molecule.
CO2
C: 4
O: 6 x 2 = 12
= 16 total val. e-

8. Drawing Lewis Structures
2) The least electronegative, non-hydrogen atom is placed in the center and the other atoms are written surrounding it. O C O

9. Drawing Lewis Structures
3) Draw single covalent bonds connecting the central atom to each outside atom.
(subtract used electrons from total) O C O 16
- 4 12

10. Drawing Lewis Structures
4) Add electrons to fill outside atom valence shells.
(substract used electrons from total) O C O 12
- 12

11. Drawing Lewis Structures
5) Check to make sure the central atom has a full octet. If not, shift pairs from outer electrons into bonds. O C O

12. Lewis Structure Practice
1) Draw a Lewis structure for NH3. H N H
False H

13. Lewis Structure Practice
2) True or False: The image below is the correct Lewis structure for PF3. F P F
True F

14. Lewis Structure Practice
3) Draw a Lewis structure for each of the following molecules:
SiO2
H2O
CH2F2
C2H4