Intermolecular Forces
and
Bonding in Solids
1
Different States of Matter
3 States
Solid state - ice
Liquid state - water
Gas state - water vapor
2
Intermolecular Forces
Intermolecular forces are forces between molecules.
Intramolecular forces hold atoms together in a molecule.
Intermolecular vs Intramolecular
•
41 kJ to vaporize 1 mole of water (inter)
•
930 kJ to break all O-H bonds in 1 mole of water (intra)
“Measure” of intermolecular force
Generally,
intermolecular
forces are much
weaker than
intramolecular
forces.
boiling point
melting point
DHvap
DHfus
DHsub
3
Intermolecular Forces
Dipole-Dipole Forces: Attractive and repulsive forces between
polar molecules
solid
liquid
4
Intermolecular Forces
Hydrogen Bond: a special dipole-dipole interaction between
the hydrogen atom in a polar N-H, O-H, or F-H bond and an
electronegative O, N, or F atom.
A
H…B
or
A
H…A
A & B are N, O, or F
5
Intermolecular Forces
Dispersion Forces: Attractive forces that arise as a result of
temporary dipoles induced in atoms or molecules
6
Dispersion Forces among Nonpolar Molecules
separated
Cl2
molecules
instantaneous
dipoles
7
Intermolecular Forces
Polarizability is the ease with which the electron distribution
in the atom or molecule can be distorted.
Polarizability increases with:
•
greater number of electrons
•
more diffuse electron cloud
Dispersion
forces usually
increase with
molar mass.
8
Intermolecular Forces
What type(s) of intermolecular forces exist between
each of the following molecules?
CH4
CH4 is nonpolar: dispersion forces.
S
SO2
SO2 is a polar molecule: dipole-dipole forces. There are
also dispersion forces between SO2 molecules.
HF
HF is a polar molecule: dipole-dipole forces. Hydrogen is
bounded to F. Hydrogen bonds exist. There are also
9
dispersion forces between HBr molecules.
Structures and Types of Solids
A crystalline solid possesses rigid and long-range order. In a
crystalline solid, atoms, molecules or ions occupy specific
(predictable) positions.
An amorphous solid does not possess a well-defined
arrangement and long-range molecular order.
A unit cell is the basic repeating structural unit of a crystalline
solid.
lattice
point
Unit Cell
Unit cells in 3 dimensions
10
Seven Types of Unit Cells
11
Three Types of Cubic Cells
1 atom/unit cell
2 atoms/unit cell
4 atoms/unit cell
(8 x 1/8 = 1)
(8 x 1/8 + 1 = 2)
(8 x 1/8 + 6 x 1/2 = 4)
12
13
The Striking Beauty of Crystalline Solids
14
Three Types of Crystalline Solids
atomic solid
ionic solid
molecular solid
15
Types and Properties of Solids
16
Metallic Crystals
•
•
•
•
Lattice points occupied by metal atoms
Held together by metallic bonds
Soft to hard, low to high melting point
Good conductors of heat and electricity
nucleus &
inner shell e-
mobile “sea”
of e17
MO Energy Levels as a Function of the # of AO
18
The band of MOs in lithium metal
Conduction
Band
Valence
Band
19
Covalent Crystals
•
•
•
•
Lattice points occupied by atoms
Held together by covalent bonds
Hard, high melting point
Poor conductor of heat and electricity
carbon
atoms
diamond
graphite
20
Graphite Consists of Layers of
Carbon Atoms
21
Electrical Conductivity in Graphite
sp2 hybridization
Delocalized p orbitals
conductor
22
Electrical Conductivity in Diamond
sp3 hybridization
localized s orbitals
insulator
23
Conductor, Semiconductor, and Insulator
conductor
insulator
semiconductor
24
Doped Semiconductors
n-type
p-type
25
Chemistry In Action: High-Temperature Superconductors
26
Acknowledgment
Some images, animation, and material have been taken from the following sources:
Chemistry, Zumdahl, Steven S.; Zumdahl, Susan A.; Houghton Mifflin Co., 6th Ed., 2003;
supplements for the instructor
General Chemistry: The Essential Concepts, Chang, Raymon; McGraw-Hill Co. Inc., 4th
Ed., 2005; supplements for the instructor
Principles of General Chemistry, Silberberg, Martin; McGraw-Hill Co. Inc., 1st Ed., 2006;
supplements for the instructor
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