Intermolecular forces are weaker than intramolecular forces but determine properties like boiling point, melting point, and density. There are several types of intermolecular forces including London dispersion forces, dipole-dipole interactions, hydrogen bonding, and ion-dipole interactions. London dispersion forces result from temporary dipoles between all molecules and increase with atomic mass. Dipole-dipole interactions occur between polar molecules while hydrogen bonding is particularly strong between a hydrogen atom bonded to an electronegative atom like nitrogen, oxygen, or fluorine. Stronger intermolecular forces require more energy to overcome.

1. Intermolecular forces
of attraction

2. Intermolecular forces are much weaker than the
intramolecular forces of attraction but are important
because they determine the physical properties of
molecules like their:
 Boiling point- temperature
 Melting point- change in temperature
 Density- weight
 Enthalpies of fusion
- The heat which a solid absorbs when it
melts.

3. Types of intermolecular forces that exist
between molecules
Dipole-dipole interactions ION-dipole interactions
London dispersion forces HYDROGEN BONDING

4. Van Der Waals Force
-Proposed by Johannes van der Waals
-distance dependent interactions.
occur when adjacent atoms come close enough
that their outer electron clouds just barely touch.
This action induces charge fluctuations that
result in a nonspecific, nondirectional attraction.
These interactions are highly distance dependent,
decreasing in proportion to the sixth power of the
separation.

5. Intermolecular force
LONDON
DISPERSION FORCE

6. • Electrons in atoms have different distributions depending on which one
you choose.
• They come in pairs and have specific energies that define the state they
are in.

7. HELIUM 1
- -

8. -
-
TEMPORARY DIPOLE
HELIUM 1

9. HELIUM 2
-
-
HELIUM 1
-
-
LONDON DISPERSION FORCE

10. LONDON DISPERSION FORCE
• Are weak attractions that results from the temporary dipoles of molecules.
All molecules have London Dispersion Forces.
• It is how nonpolar molecules can be attracted to each other.
• MIGHT be called van der Waals by other sources.
• How noble gases can have other states.
• Weaker as distance increases.
• Proposed by Fritz London

11. LONDON DISPERSION FORCE increases with increasing atomic
mass.

12. Intermolecular force
Dipole-Dipole Force

13. Polar molecules have a slightly
positive side and a slightly negative
side.

14. • The attraction of bond dipoles
(Unequal sharing of electons)
from covalently bonded atoms.
• Only polar molecules.
• Stronger than London Dispersion
Forces.

15. Intermolecular force
ion-Dipole Force

16. ION POLAR
SLIGHT
SLIGHT
Ion-Dipole Force
• electrostatic interaction
involving a partially charged
dipole of one molecule and a
fully charged ion
• strength of the force is
proportionate to ion charge

17. Intermolecular force
Hydrogen bonding

18. Hydrogen Bonding
• forces created when a hydrogen atom bonded to an electronegative atom
approaches a nearby electronegative atom
• a relatively strong force of attraction between molecules
• greater electronegativity of the hydrogen bond acceptor will create a
stronger hydrogen bond

19. Intermolecular
force
Occurs between … Relative strength
Dipole-dipole
attraction
Partially
oppositely
charged ions
Strongest
Hydrogen
bonding
H atom and , N,O
or F atom
As strong as
dipole-dipole
attraction
London
dispersion
attraction
Temporary or
induced dipoles
Weakest
Relative strength of intermolecular forces of
attraction

20. How forces of
attraction affect
properties of
compounds?
the stronger the
intermolecular forces of
attraction,
the more energy is required to
break those forces

21. QUIZ

22. 1-3
Physical properties that are
determined/affected by
intermolecular forces.

23. 4
Give one element where
Hydrogen Atom can be
bonded by Hydrogen Bonding.

24. 5
Proponent of the distance
dependent interactions.

25. 6
Proponent of the London
Dispersion Force.

26. 7
Identify the type of the
intermolecular force.
H2S

27. 8
Identify the type of the
intermolecular force.
H2O

28. 9
Identify the type of the
intermolecular force.
HCl

29. 10
BONUS 

30. answErs
1-3: BOILING POINT, Melting point, Density, enthalpies of fusion
and vaporization
4: OXYGEN, Nitrogen, Fluorine
5: Johannes van der waals
6: Fritz London
7: London dispersion force
8: HYDROGEN BONDING
9: DIPOLE-DIPOLE
10:BONUS