General Chemistry: Chapter 12 Ozone 4 electrons left to fill the 3 molecular orbitals made from the combination of the 3 perpendicular p orbitals. BONDING-0 nodes ANTI-BONDING-2 nodes NON-BONDING-1 node, Basically this non-bonding orbital contains 0 contribution from the centre oxygen atom. Bonding Anti-bonding Non-bonding Prentice-Hall © 2002 General Chemistry: Chapter 12

Chemistry 140 Fall 2002 Band Theory Valence band and conducting band are separated by a small energy gap thereby allowing electrons to jump to conduction band. Valence band is only partially filled. Conducting band is also the valence band Valence band and conducting band are separated by a large energy gap. Gap too large to allow electrons to jump. Valence band and conducting band overlap Some metals the valence band is only partially filled thus the conducting band is also the valence band Some metals have a filled valence band, but the conducting band overlaps and still conducts Semiconductor has the valence and conducting band separate. The application of heat can provide the energy required to put electrons into the conducting band Insulators have an energy gap that is so wide, electrons are not promoted into the conducting band. Electricity does not go! Prentice-Hall © 2002 General Chemistry: Chapter 12

Semiconductors P energy level Al energy level Chemistry 140 Fall 2002 Semiconductors P energy level Al energy level Intrinsic semiconductors: fixed band gap [CdS (yellow), GaAs (black)] Intrinsic semiconductors: fixed band gap. Ex. CdS, absorbs violet light and some blue, reflects less energetic light. Thus looks bright yellow. GaAs, small band gap, all visible light is absorbed, looks black. Extrinsic semiconductors: band gap is controlled by addition of impurities – doping. Energy level of P is just below the conduction band of Si. P uses four of five electrons to bond to Si, one left over can be donated. n-type semiconductor – n refers to negative, the type of charge that is MOBILE. Energy level of Al is just above the valence band. Electrons can move into the Al orbital and leave a HOLE in the valence band. Positive charge can move around thus this is a p-type semiconductor. Silicon can be doped with an acceptor or donor atoms Silicon doped with Phosphorus, the conduction band is just above the donor band, electrons are easily promoted (n-type) Silicon doped with Al, results in an acceptor level that removes electrons, leaving positive holes (p-type) Extrinsic semiconductors: band gap controlled by addition of impurities (process called doping) Prentice-Hall © 2002 General Chemistry: Chapter 12

General Chemistry: Chapter 12 Chapter 12 Questions 1, 3, 8, 10, 16, 17, 18, 29, 33, 39, 40, 45, 59, 68, 72, 76 Prentice-Hall © 2002 General Chemistry: Chapter 12

Chapter 13: Liquids, Solids and Intermolecular Forces Chemistry 140 Fall 2002 General Chemistry Principles and Modern Applications Petrucci • Harwood • Herring 8th Edition Chapter 13: Liquids, Solids and Intermolecular Forces Philip Dutton University of Windsor, Canada N9B 3P4 Prentice-Hall © 2002 (modified 2003 by Dr. Paul Root and 2005 by Dr. David Tramontozzi) Thermochemistry branch of chemistry concerned with heat effects accompanying chemical reactions. Direct and indirect measurement of heat. Answer practical questions: why is natural gas a better fuel than coal, and why do fats have higher energy value than carbohydrates and protiens.

General Chemistry: Chapter 12 Chemistry 140 Fall 2002 Contents 13-1 Intermolecular Forces and some Properties of Liquids 13-2 Vaporization of Liquids: Vapor Pressure 13-3 Some Properties of Solids 13-4 Phase Diagrams 13-5 Van der Waals Forces 13-6 Hydrogen Bonding 13-7 Chemical Bonds as Intermolecular Forces 13-8 Crystal structures 13-8 Energy Changes in the Formation of Ionic Crystals Focus on Liquid Crystals Physical Chemistry / Inorganic chemistry Prentice-Hall © 2002 General Chemistry: Chapter 12

13-1 Intermolecular Forces and Some Properties of Liquids Cohesive Forces Intermolecular forces between like molecules. Adhesive Forces Intermolecular forces between unlike molecules. Surface Tension  Energy or work required to increase the surface area of a liquid. Viscosity  A liquids resistance to flow Prentice-Hall © 2002 General Chemistry: Chapter 12

Intermolecular Forces Chemistry 140 Fall 2002 Intermolecular Forces Interactions with molecules on each side (surface tension) Interactions with molecules surrounding (viscosity) Molecules on the top are attracted by molecules on each side an below (surface tension) Molecules in the middle are attracted by molecules that surround it on all sides (viscosity) Prentice-Hall © 2002 General Chemistry: Chapter 12

Intermolecular Forces Clean glass Oil covered glass Adhesive forces between water and glass cause meniscus to form. Hg metallic bonds are stronger than adhesive forces with glass therefore no meniscus forms. Capillary action Prentice-Hall © 2002 General Chemistry: Chapter 12