The document discusses intermolecular forces of attraction between molecules. It begins by introducing the topic and noting that intermolecular forces determine properties like boiling points. It then defines the main types of intermolecular forces - London dispersion forces, dipole-dipole forces, ion-dipole forces, and hydrogen bonding. The document spends several paragraphs explaining each type of intermolecular force in more detail. It concludes by discussing how to predict the intermolecular forces that will be present between different molecules.

1. General Chemistry 2
Science, Technology, Engineering, and Mathematics
Lesson 1.2
Intermolecular Forces
of Attraction

2. 2
2
Have you ever wondered why some substances boil
easier than others?

3. 3
3
For example, liquid
nitrogen when
exposed to room
temperature
immediately turns
into vapor.

4. 4
4
On the other hand, water needs to be heated first to be
converted to steam.

5. 5
The kinetic molecular
theory states that
matter is composed
of tiny particles that
carry energy, interact
with one another and
are in constant
random motion.
particles in a gas

6. 6
6
The interaction between particles and their strength
determines certain properties for that matter.

7. 7
What are the different types
of intermolecular forces of
attraction?

8. Learning Competencies
At the end of the lesson, you should be able to do the following:
8
● Describe and differentiate the types of
intermolecular forces (STEM_GC11IMF-IIIa-c-
100).
● Predict the intermolecular forces possible for a
molecule (STEM_GC11IMF-IIIa-c-101).

9. Learning Objectives
At the end of the lesson, you should be able to do the following:
9
● Differentiate the different types of intermolecular
forces of attraction.
● Predict the intermolecular forces that may exist
for a molecule.

10. Learning Objectives
At the end of the lesson, you should be able to do the following:
10

11. 11
● Intermolecular forces are attractive forces present in
between molecules.
● The four main types of intermolecular forces are:
○ London dispersion forces,
○ dipole-dipole forces,
○ ion-dipole forces, and
○ hydrogen bonding forces
Intermolecular Forces of Attraction

12. 12
London dispersion forces and dipole-dipole forces are
collectively known as van der Waals forces of attraction.
Intermolecular Forces of Attraction
Johannes van der Waals

13. 13
Ion-ion interaction is the interaction between two
oppositely charged particles.
Ion-Ion interactions
cation
positively
charged sodium
ion (Na+)
anion
negatively
charged
chloride ion (Cl–)

14. 14
Ion-ion interaction is also known as ionic bonds.
Ion-Ion interactions
table salt sodium and chloride ions

15. Remember
15
Ion-ion interactions are between
electrically charged particles.

16. 16
Ion-Dipole interactions
ion-dipole interactions strengths of ion-dipole interactions

17. 17

18. 18
This type of interaction is responsible for the dissolution of most ionic
solids in polar solvents.
Ion-Dipole interactions

19. Remember
19
The partially positive end of the polar
molecule interacts with the anion,
whereas the partially negative end of
the polar molecule interacts with the
cation.

20. 20
Present in polar molecules which are described as dipoles
Dipole-Dipole interactions
Hydrochloric acid is a dipole.

21. 21

22. 22
Dipole-dipole forces
Dipole-dipole interactions are the
strongest intermolecular force
of attraction.

23. 23
The dipole-dipole force
exists between the
partially positive end of
one HCl molecule and
the partially negative
end of another HCl
molecule.

24. 24
An attractive force that exists when hydrogen is bonded to
the most electronegative atoms, namely F, O, or N
Hydrogen Bonding
Hydrogen bonding between formaldehyde and water

25. 25
Hydrogen bonding
Hydrogen bonding is a relatively strong
force of attraction between molecules, and
considerable energy is required to break
hydrogen bonds.
This explains the exceptionally high boiling
points and melting points of compounds
like water and hydrogen fluoride.

26. 26

27. Many unusual
properties of water
are attributed to
hydrogen bonding.
In water, the
hydrogen of one
molecule is attracted
to the oxygen atom
of another molecule.
27

28. Remember
28
Hydrogen bonding can only be
exhibited when one molecule has a
hydrogen atom is directly bonded to
fluorine, oxygen or nitrogen atom.

29. 29
● The weakest type of IMFA and are present in between all
electrically neutral molecules
● Named after the German-American physicist Fritz
London
London Dispersion Forces
Temporary dipoles between nonpolar molecules

30. 30
A nonpolar molecule has an equal distribution of charges.
London Dispersion Forces
(a) (b) (c)

31. 31
At any instant, an instantaneous dipole may form.
London Dispersion Forces
(a) (b) (c)

32. 32
The instantaneous dipole may induce the formation of
another dipole (induced dipole).
London Dispersion Forces
(a) (b) (c)

33. The formation of instantaneous dipole can be observed in
nonpolar molecules such as O2.
33

34. 34
London Dispersion Forces

35. 35
London Dispersion Forces

36. Remember
36
All electrically neutral molecules exhibit
London dispersion forces (LDF).

37. Let’s Sum It Up!
37

38. 38
Induced Dipoles

39. 39
How are induced dipoles
created?

40. 40
Predicting Intermolecular Forces of Attraction
Recall that compounds can be classified as ionic or
covalent based on the types of bonds present.
● Ionic compounds ⟶ ion-ion interactions
● Covalent compounds ⟶ depend on polarity

41. 41
Predicting Intermolecular Forces of Attraction
● The strength of the ion-ion interaction is governed by
Coulomb's law
where F is coulombic force, q1 and q2 are the charges
of the particles, and r is the distance between the
particles.

42. 42
Predicting Intermolecular Forces of Attraction
Compound Melting
Point
(OC)
Compound Melting
Point
(OC)
Compound Melting
Point
(OC)
NaF 993 CaF2 1423 MgO 2800
NaCl 801 Na2S 1180 CaO 2580
NaBr 747 K2S 840 BaO 1923

43. 43
Predicting Intermolecular Forces of Attraction
● Covalent bonds, on the other hand, involve the
sharing of electrons between two nonmetal atoms.
● Recall that polarity of the molecule can be determined
by identifying the polarity of the bonds and the
molecular geometry for the compound.

44. 44
Predicting Intermolecular Forces of Attraction
● Polar covalent compounds are molecules with a net
dipole moment due to unequal sharing of electrons
between the atoms.
● This causes the molecule to have a partial positive (δ+)
and a partial negative (δ-) charges, which are also
known as a dipole.

45. 45
Predicting Intermolecular Forces of Attraction
● Polar covalent compounds can either have dipole-
dipole interactions or hydrogen bonding, depending
on the presence of H and its connectivity to other
atoms in the compound, and London dispersion
forces.

46. Notice that H2O,
HF, and NH3
have higher
boiling points
than the rest of
their groups
because they
can form
hydrogen
bonding.
46

47. Remember
47
Some molecules have polar bonds but
are nonpolar as a whole. This is due to
the cancellation of the dipole moment
due to the molecular geometry.

48. 48
Predicting Intermolecular Forces of Attraction
● Nonpolar covalent compounds are molecules with
zero dipole moment due to equally shared electrons
between the atoms.
● The only intermolecular force present in these
compounds is the London dispersion forces.

49. 49
Predicting Intermolecular Forces of Attraction
Polarizability is the measure of how easy it is to distort
the electron distribution of a molecule.
Compound
Polarizability,
10–25 cm3
Molar Mass,
amu
Boiling Point,
K
H2 7.9 2.02 20.35
O2 16.0 32.00 90.19
N2 17.6 28.01 77.35

50. 50
Predicting Intermolecular Forces of Attraction

51. 51
Predicting Intermolecular Forces of Attraction

52. 52
How can one determine the
intermolecular force present for
a molecule?

53. Tips
53
In order to predict the intermolecular
forces between two molecules, you
must first determine the type of
compound present.

54. Let’s Sum It Up!
54
● Intermolecular forces of attraction are attractive
forces present in between molecules.
○ Ion-ion interaction is the interaction between
oppositely charged particles.
○ Ion-dipole interaction results from the
electrostatic attraction of a molecule
containing a dipole and an ion.

55. Let’s Sum It Up!
55
● Intermolecular forces of attraction are attractive
forces present in between molecules.
○ Dipole-dipole interactions are attractive forces
that are a moderately strong type of IMFA and
are present in between polar molecules.
○ Hydrogen bonding is a special kind of dipole-
dipole force that exists when hydrogen is
bonded to the most electronegative atoms,
namely F, O, or N.

56. Let’s Sum It Up!
56
● Intermolecular forces of attraction are attractive
forces present in between molecules.
○ London dispersion forces (LDFs) are the
weakest type of IMFA and are present in
between all electrically neutral molecules―polar
and nonpolar molecules.
○ Induced dipoles occur when a nonpolar atom
becomes polar due to the presence of an ion or
a dipole.

57. Let’s Sum It Up!
57
● The strength of ion-ion interactions is dependent
on the coulombic force between the particles. It is
directly proportional to the product of the charges
and inversely proportional to the distance between
the particles.

58. Let’s Sum It Up!
58
● The strength of ion-dipole interactions depends on
the charge of the ion present.
● The strength of LDFs depends on the polarizability
of the molecule.
● Polarizability refers to the ease at which the
electron cloud can be distorted.

59. Challenge Yourself
General Chemistry 2: 8.4. Calorimetry: Measurements of Energy 59
59
Arrange the following in increasing IMFA
strength: ethanol, ethylene glycol, and ethane.
Ethanol C₂H₆O
Ethylene glycol C₂H₆O₂
Ethane C₂H₆

60. Challenge Yourself
General Chemistry 2: 8.4. Calorimetry: Measurements of Energy 60
The strongest IMFA present in ethanol and
ethylene glycol is hydrogen bonding due to the
presence of the -OH group. However, there are
two -OH groups present in ethylene glycol, which
makes its IMFA stronger than ethanol. Ethane, on
the other hand, is a nonpolar molecule; therefore,
the strongest IMFA that will exist is the London
dispersion force.

61. Bibliography
61
Brown T.L. et al. 2012. Chemistry: The Central Science. Pearson Prentice Hall.Brown. Chemistry: The
Central Science. Prentice-Hall, 2005.
Bettelheim, Frederick A., et al. 2015. Introduction to General, Organic and Biochemistry. Boston:
Cengage Learning.
Ebbing, Darrell and Steven Gammon. 2016. General Chemistry. Boston: Cengage Learning.
Moore, John W, and Conrad L. Stanitski. 2015. Chemistry: The Molecular Science, 5th ed. USA: Cengage
Learning.
Petrucci, Ralph H. General Chemistry: Principles and Modern Applications. Toronto, Ont.: Pearson
Canada, 2011. Print.

62. Bibliography
62
Reger, Daniel L., et al. 2009. Chemistry: Principles and Practice. Boston: Cengage Learning.
Silberberg, Martin S. 2007. Principles of General Chemistry. McGraw-Hill Company. 2007
Spencer, James N., et al. 2010. Chemistry: Structure and Dynamics. New Jersey: John Wiley & Sons.