Polarity
What are the similarities and differences
between polar and nonpolar molecules?
CH 8.4
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)
Results in Hydrogen Bonds in water
Helps water form
“skin” called surface
tension. Very
important for
Biology and life
Electronegativity
pg
177
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
Like dissolves in Like
Polar/charged substances dissolve in polar
liquids
Table salt (NaCl) dissolves in water as Na+
and Cl-
Nonpolar Covalent Bonding
●
●
●
●
electrons shared
both atoms want electrons the same amount
no difference in electronegativity
eg Cl2
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)
Alkanes are nonpolar
Even though Carbon is slightly more
electronegative than Hydrogen…
There is no (-) or (+)
end/pole
pg 238
Bond Types
Difference in Electronegativity
Type of Bond
Example
0-0.4
Nonpolar covalent
H--H
0.4-1.0
Moderately polar covalent
H--Cl
1-2
Very polar covalent
H--F
2+
Ionic
NaCl
Review:
Due Wednesday:
p238-244 #30-37
p706-707 #18-25
p711 #26-29