Name ______________________________________
Period __________
Date ____________________________
KSJC Chemistry
Unit 2 – Chemical Bonding
Objectives:
SWBAT define polarity and identify polar and non-polar compounds.
SWBAT determine the effect of polarity on intermolecular forces.
Criteria for Success:
I can determine the polarity of different compounds using Lewis structures and electronegativity.
I can determine the effect of polarity on dipole-dipole forces and hydrogen bonding.
Agenda:
HW Review (10 min)
Review: Polarity (10 min)
Determining Polarity of Compounds from Lewis Structures (15 min)
Intermolecular Forces: Dipole-Dipole (5 min)
Intermolecular Forces: Hydrogen Bonding (15 min)
Intro to Polarity:
1) Draw the Lewis dot structure for HCl:
Now check out this adorable comic of a polar bear and
a penguin:
2) If the penguin represents a hydrogen atom and the polar
bear represents a chlorine atom, what does the ice cream
represent in the drawing? What do you think the picture is
trying to illustrate?
3) This point of this comic is to introduce the concept of polarity. Based on just this intro, what do you
think polarity is?
Polarity
Order the following bonds in order from most polar to least polar: nonpolar covalent, ionic, polar
covalent
____________________________  _____________________________  _____________________________
BUT WHY????
Electronegativity
Equal Desire:
Stronger Desire:
POLARITY
Polar
HX (ex. HCl, HF, HI)
H2O
NH3
Molecules are polar because…
1.
2.
Molecules are non-polar because…
1.
2.
3.
Non-polar
X2 (ex. H2, Cl2, I2)
CO2
CX4 (ex. CH4, CCl4, CI4)
Four Steps to Determine Polarity!
Step 1: Draw it.
Step 2: Check for lone
pairs. If unevenly
present, POLAR. If not
present, GO TO STEP 3.
NH3
Step 3: Check dipoles. If
symmetrical,
NONPOLAR. If
asymmetrical, POLAR.
Step 4: Polar or
Nonpolar?
CI4
CO2
NCl3
HI
Br2
These are all what kind of bonds? Ionic or covalent?
Types of Intermolecular Forces:
1. Dipole-dipole interaction
o All POLAR molecules have dipole-dipole interactions

Remember: polarity is caused by the UNEQUAL sharing of electrons between atoms
with different ELECTRONEGATIVE values.

The more polar a molecule is, the STRONGER the dipole-dipole interaction.
Practice:
a) Please circle if the molecule listed are polar
HBr
H2O
CH4
F2
SH2
H2Se
State whether or not the following molecules/compounds will have dipole-dipole forces
Bond
Yes or no (dipole-dipole)
O2
H2Te
H2S
HI
CH4
CO2
2. HYDROGEN BONDING
o Stronger than dipole-dipole interactions
o Interaction between partially positive and a partially negative atom like ________, ___________, or
____________.
Example: Hydrogen bonding in H2O
The higher the boiling point, the stronger the intermolecular forces!
WHY?
Practice:
1. In which liquid is hydrogen bonding the most significant form of attraction?
(1) HF
(2) HCl
(3) HBr
(4) HI
Explanation: _________________________________________________________________________
_____________________________________________________________________________________
2. Hydrogen bonding is strongest between molecules of
(1) H2S
(2) H2O
(3) H2Se
(4) H2Te
Explanation: _________________________________________________________________________
_____________________________________________________________________________________
3. Which atom has the least attraction for the electrons in a bond between that atom and an atom of hydrogen?
(1) carbon
(2) nitrogen
(3) oxygen
(4) fluorine
Explanation: _________________________________________________________________________
_____________________________________________________________________________________
4. The unusually high boiling point of water is due to the
(1) network bonds between the molecules
(2) hydrogen bonds between the molecules
(3) linear structure of the molecules
(4) nonpolar character of the molecule
Explanation: _________________________________________________________________________
5. Base the next two questions on this table below:
a) Explain, in terms of electronegativity differences, why the bond in H—Cl is more polar than the bond in
H—I.
b) Explain, in terms of intermolecular
forces, why hydrogen has a lower
boiling point that hydrogen
bromide.
6. Each molecule listed below is
formed by sharing electrons between atoms when the atoms within the molecule are bonded together.
Molecule A: Cl2
Molecule B: CCl4
Molecule C: NH3
a) Draw the electron-dot structure for the NH3 molecule
b) Explain why CCl4 is classified as a nonpolar molecule.
c) Explain why NH3 has stronger intermolecular forces of attraction than Cl2.
d) Explain how the bonding for KCl is different from the bonding in molecule A, B, C.
Name _________________________________________
Period ___________
Date ______________________
KSJC Chemistry Homework
1. Explain in terms of electronegativity difference, why the bond in a molecule of HF is more polar than
the bond in a molecule of HI.
2. Draw a Lewis electron-dot diagram for CF4.
3. What is the total number of electron pairs shared between the carbon atoms and one of the oxygen
atoms in a carbon dioxide molecule, CO2? Show your work to receive full credit!
4. Explain in terms of subatomic particles (neutrons, protons, and electrons), why the size of a chloride
ion is larger than the size of a neutral chlorine atom. Think about the number of valence electrons each
has.
5. The electrons in a bond where two iodine atoms (I2) are shared
a. equally, and the resulting bond is polar
b. equally, and the resulting bond is nonpolar
c. unequally, and the resulting bond is polar
d. unequally, and the resulting bond is nonpolar
6. Which bond is most polar?
a. H-F
b. H-Cl
c. H-Br
d. H-I
7. What is the difference between a polar covalent bond and a covalent bond?
8. What is the difference between covalent and ionic bonds?
9. Explain the steps you would go through to decide if GeBr4 is a polar or nonpolar covalent molecule. BE
SPECIFIC SO THAT ANYONE CAN FOLLOW YOUR LOGIC!
If extra time: ask these questions for students to answer as partners on whiteboards!
1. The electrons in a bond between two iodine
atoms (I2) are shared
1.
2.
3.
4.
equally, and the resulting bond is polar
equally, and the resulting bond is nonpolar
unequally, and the resulting bond is polar
unequally, and the resulting bond is
nonpolar
2. Which diagram best represents a polar molecule?
1.
3.
2.
4.
3. Which structural formula represents a linear
nonpolar molecule containing two polar bonds?
1.
3.
2.
4.
4. Which electron-dot formula represents a polar
molecule?
5. Which structural formula represents a nonpolar
molecule?
1.
3.
2.
4.
6. Which combination of atoms can form a polar
covalent bond?
1.
2.
3.
4.
H and H
H and Br
N and N
Na and Br
7. Which molecule contains a polar covalent bond?
1.
3.
2.
4.
8. Which bond is most polar?
1.
2.
3.
4.
H-F
H-Cl
H-Br
H-I
9. Which electron-dot structure represents a nonpolar molecule?
1.
3.
2.
4.
1.
3.
4. CO2(s)
12. Which molecule is nonpolar?
2.
4.
1.
2.
3.
4.
H2O
NH3
CO
CO2
13. Which type of molecule is CF4?
10. Which structural formula represents a dipole?
1. polar, with a symmetrical distribution of
charge
2. polar, with an asymmetrical distribution of
charge
3. nonpolar, with a symmetrical distribution of
charge
4. nonpolar, with an asymmetrical distribution
of charge
14. Which formula represents a polar molecule?
1.
3.
2.
4.
11. Which of the following solids has the highest
melting point?
1. H2O(s)
2. Na2O(s)
3. SO2(s)
1.
2.
3.
4.
Br2
CO2
CH4
NH3
15. At standard pressure, a certain compound has a
low boiling point and is insoluble in water. At STP,
this compound most likely exists as
1.
2.
3.
4.
ionic crystals
metallic crystals
nonpolar molecules
polar molecules