Transcript No Slide Title

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
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Intermolecular Forces
Dispersion Forces: Attractive forces that arise as a result of
temporary dipoles induced in atoms or molecules
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Dispersion Forces among Nonpolar Molecules
separated
Cl2
molecules
instantaneous
dipoles
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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.
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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
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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)
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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
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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
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The band of MOs in lithium metal
Conduction
Band
Valence
Band
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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
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Graphite Consists of Layers of
Carbon Atoms
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Electrical Conductivity in Graphite
sp2 hybridization
Delocalized p orbitals
conductor
22
Electrical Conductivity in Diamond
sp3 hybridization
localized s orbitals
insulator
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Conductor, Semiconductor, and Insulator
conductor
insulator
semiconductor
24
Doped Semiconductors
n-type
p-type
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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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