Intermolecular Forces and Bonding in Solids

1. Intermolecular Forces and Bonding in Solids

2. Different States of Matter 3 States Solid state - ice Liquid state - water Gas state - water vapor

3. Generally, intermolecular forces are much weaker than intramolecular forces. 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

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

5. or … … H H B A A A 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 & 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. separated Cl2 molecules Dispersion Forces among Nonpolar Molecules instantaneous dipoles

8. Dispersion forces usually increase with molar mass. 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

9. O O S Intermolecular Forces What type(s) of intermolecular forces exist between each of the following molecules? CH4 CH4 is nonpolar: dispersion forces. 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. lattice point 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 amorphoussolid 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. Unit cells in 3 dimensions Unit Cell

11. Seven Types of Unit Cells

12. Three Types of Cubic Cells 4 atoms/unit cell 2 atoms/unit cell 1 atom/unit cell (8 x 1/8 + 6 x 1/2 = 4) (8 x 1/8 + 1 = 2) (8 x 1/8 = 1)

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. nucleus & inner shell e- mobile “sea” of e- 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

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

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

20. carbon atoms Covalent Crystals • Lattice points occupied by atoms • Held together by covalent bonds • Hard, high melting point • Poor conductor of heat and electricity graphite diamond

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 conductor insulator semiconductor

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