Bonding
What exactly is a bond? Depends…Ionic or Covalent? Polar?
NON-POLAR COVALENT=> equal sharing of electron pair
0 < ∆EN < 0.4
POLAR COVALENT= unequal sharing of electron pairs, e-’s
spend more time closer to one atom, 0.4 < ∆EN < 1.7
IONIC “BOND”= transfer of electrons, no physical
connection to one another, atoms are held together by
an electrostatic attraction, ∆EN > 1.7
Molecular Polarity
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Tutorial 1: p. 226
Figure 6: p. 228
p. 227 #1,2
HW: p. 229 #1-7ab
No molecular dipole
=> non-polar molecule
Molecular Dipole is present
=>
molecule
No polar
molecular
dipole
=> non-polar molecule
Molecular Dipole is present
=> polar molecule
Which process requires more energy?
Why?
H2O(l)  H2O(g)
or
2 H2O(l)  2 H2(g) + O2(g)
Intermolecular Forces
London force (dispersion)
•due to electrostatic
attraction b/w protons in one
molecule and electrons of
neighbouring molecules
•strength α # of e-
Intermolecular Forces
dipole-dipole force
•due to attraction of one
dipole by surrounding dipoles
•strength α molecular
polarity
Intermolecular Forces
Hydrogen bonding
•due to attraction of a H
bonded to a highly EN atom
(O, N or F) in one molecule by
the lone pair of e- on a highly
electronegative atom of a
neighbouring molecule
H2Te
H2Se
H2S
H2O
bp = -10°C
bp = -50°C
bp = -80°C
bp = 100°C
List all IMF for each substance.
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O2(g)
Cl2O(g)
H2O(l)
CH4(g)
CH3Cl(g)
Arrange from lowest to highest bp.
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H2O
CH4
CH3Cl
NH3
CH3OH
H2
C3H8
Explain each statement.
• Water has a much higher bp than methane.
• Bromine is a liquid at room temperature
while chlorine is a gas.
• CHCl3 has a higher bp than CCl4.
Properties of Ionic and Molecular
Compounds
Create a table to compare the following properties
of ionic and molecular compounds. (p. 69)
• state
• solubility in water
• electrical conductivity as a solid
• electrical conductivity in aqueous solution
• melting point
• boiling point
Intermolecular Forces and States
Melting/Boiling Point
Solubility in Water
Low Conductivity of Covalent Compounds
What is conductivity?
What is electricity?
Are the e- free to move in covalent
bonds? Why or why not?
Covalent compounds include
fats and oils
Which elements form covalent
bonds? Do these usually
conduct electricity?
Conductivity of Ionic Compounds
Is there an actual bond between ionic
compounds?
Ionic compounds are held together by
electrostatic attractions
The lack of physical bonds between
ions means that electricity can be
conducted through ionic compounds
What types of elements form ionic
compounds? Do these elements
usually conduct electricity?
Properties of Liquids
Cohesive forces:
• attractions b/w like
molecules
Adhesive forces:
• attractions b/w unlike
molecules
Extra Practice for the Unit Test
• There are Self-Quizzes at the end of each chapter
and unit which provide further practice of concepts.
Answers are provided in the back of the text book.
For this unit, try Chapters 1-3 and Unit 1 SelfQuizzes.
• Unit 1 Review p. 138 #4,6-16,18-20,22,23,25,26,2831,34-42,46-50,54-56,58,62-66,71-74