1. Polarity
What are the similarities and differences between polar and nonpolar molecules?
CH 8.4

2. Polarity
When one atom is more electronegative than another atom. The “stronger” atom can pull the shared electrons closer, making it slightly negative. This leaves the other atom slightly positive.
EX: H2O
(covalent bond)

3. Results in Hydrogen Bonds in water
Helps water form
“skin” called surface
tension. Very
important for
Biology and life

4. Electronegativity
pg 177

5. Ionic Bonding Pull so strong that electrons given and taken
one atom wants the electrons more, pulls harder
Uneven distribution of electrons
Due to a large difference in electronegativity
eg NaCl
Na Cl
Na Cl

6. Like dissolves in Like
Polar/charged substances dissolve in polar liquids
Table salt (NaCl) dissolves in water as Na+ and Cl-

7. Nonpolar Covalent Bonding
electrons shared
both atoms want electrons the same amount
no difference in electronegativity
eg Cl2

8. Why do we care?
Like Dissolves Like = only materials with positive and negative parts will dissolve in water
Nonpolar molecules will NOT dissolve in water (oil and water for example)

9. Alkanes are nonpolar
Even though Carbon is slightly more electronegative than Hydrogen…
There is no (-) or (+)
end/pole

10. Bond Types pg 238 Difference in Electronegativity Type of Bond Example
0-0.4
Nonpolar covalent
H--H
Moderately polar covalent
H--Cl
1-2
Very polar covalent
H--F 2+
Ionic
NaCl

11. Review:

12. Due Wednesday:
p #30-37
p #18-25
p711 #26-29