1. Polarity & Lewis Structures

2. Bonds Non-polar covalent – EN difference is 0-0.3
Ionic Bonds- EN difference greater than 1.7

3. Polarity
δ+ or δ-
H-F bond (electronegativity-H: 2.1and F: 4.0), calculate the difference, the more electronegative atom gets the δ negative charge

4. Examples H—Cl H—C H—H H—O S—Cl Ca and Cl C and S Mg and F N and O
H—H
H—O
S—Cl
Ca and Cl
C and S
Mg and F
N and O
O and H
S and O

5. Lewis Structure- Covalent Bonds
Shows how valence electrons (v.e.) are shared in a molecule

6. Types of Covalent Bonds
Single Bond- 2 ve-
Double Bond – 4 ve-
Triple Bond- 6 ve-

7. Octet Rule All atoms want 8 ve- EXCEPT: H- 2ve- and B- 6ve-
There are other exceptions such as S and P

8. How to draw Lewis Structure Step 1
Determine the total number of valence electrons
Ex. NF3

9. Step 2
Arrange atoms
If there is a carbon in the molecule, carbon will be in the center.
If there is no carbon then the least electronegative atom will go in the center
The remaining atoms will surround the center atom

10. Step 3 Bond all atoms at least once
Bonding is sharing one valence electron from each atom- uses 2 valence electron
Place remaining valence electrons to go around the most electronegative atoms first to agree with octet rule, if extra v.e. put on the remaining atoms

11. Step 4 Check and make sure all atoms follow the octet rule
If not, put in multiple bonds

12. Ionic Bonds
Shows the transfer of electrons

13. Determining Lewis Structure
1st – Write out each atom in the chemical formula- Remember the subscript= the # of atoms
2nd – Draw dot structure
3rd -Remove valence electrons from metal and give them to nonmetal using arrows
4th - Write the charges on atoms and new dot structure
Example NaCl, MgCl2, and Na2O