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Intermolecular Forces and

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Presentation on theme: "Intermolecular Forces and"— Presentation transcript:

1 Intermolecular Forces and
Bonding in Solids

2 Different States of Matter
Solid state - ice Liquid state - water Gas state - water vapor

3 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 boiling point melting point DHvap DHfus DHsub Generally, intermolecular forces are much weaker than intramolecular forces.

4 Intermolecular Forces
Dipole-Dipole Forces: Attractive and repulsive forces between polar molecules solid liquid

5 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 & B are N, O, or F

6 Intermolecular Forces
Dispersion Forces: Attractive forces that arise as a result of temporary dipoles induced in atoms or molecules

7 Dispersion Forces among Nonpolar Molecules
separated Cl2 molecules instantaneous dipoles

8 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.

9 Intermolecular Forces
What type(s) of intermolecular forces exist between each of the following molecules? CH4 CH4 is nonpolar: dispersion forces. S O 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 dispersion forces between HBr molecules.

10 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

11 Seven Types of Unit Cells

12 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)


14 The Striking Beauty of Crystalline Solids

15 Three Types of Crystalline Solids
atomic solid ionic solid molecular solid

16 Types and Properties of Solids

17 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 e-

18 MO Energy Levels as a Function of the # of AO

19 The band of MOs in lithium metal
Conduction Band Valence Band

20 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

21 Graphite Consists of Layers of Carbon Atoms

22 Electrical Conductivity in Graphite
sp2 hybridization Delocalized p orbitals conductor

23 Electrical Conductivity in Diamond
sp3 hybridization localized s orbitals insulator

24 Conductor, Semiconductor, and Insulator

25 Doped Semiconductors n-type p-type

26 Chemistry In Action: High-Temperature Superconductors

27 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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