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Unformatted text preview: Classes of Materials SOLIDS: Structure and Bonding Molecular Ionic Covalent network Metals (alloys) Bonding in Solids 1 Review from Chem 110 Chapter 8, 11 Intra- vs. Inter-molecular forces Hold together atoms in a molecule or compound Intramolecular forces Hold together molecules in a gas, liquid, or solid Intermolecular forces Breaking bonds (interacHons) _______________ energy Forming bonds (interacHons) _______________ energy Bonding in Solids 2 Review from Chem 110 Chapter 11 TYPES OF INTERMOLECULAR FORCES Depends on Q Q, Q, , direcHonal dipole-dipole Ion-Ion ionic bond Ion-Dipole Ions in aqueous soluHons of electrolytes Dipole-Dipole Ion-Induced Dipole ions in nonpolar solvents Dipole-Induced Dipole polar molecules in nonpolar solvents Dispersion induced-dipole induced dipole Hydrogen Bonding must have H bonded to N,O,F Bonding in Solids 3 Review from Chem 110 Chapter 11 Phase Diagrams Plot of pressure vs. temperature of the system showing the boundaries between the phases. normal melHng point pressure dependence of melHng point normal boiling point pressure dependence of boiling point criHcal point triple point supercriHcal fluid coexistence curves What happens when the pressure and/or temperature of the system is changed? Bonding in Solids 4 Specific examples: Phase diagram of H2O Review from Chem 110 Chapter 11 Solids, liquids, and gases Bonding in Solids 5 Intermolecular forces & BPs Boiling point: temperature required to break all intermolecular aQracHons (vaporize) Type Example BP(C) Covalent C(graphite) 4827 Metal Fe 2750 Ion-ion NaCl 1413 H-bonding H2O 100 Dipole- Dipole CHF3 -82 London Dispersion CF4 -129 What does this imply about bonding in solids? Bonding in Solids 6 The chemistry of solids How are atoms arranged in solids? Structure How are the atoms held together in solids? Bonding How do classes of solids differ because of their bonding? Atomic Molecular Covalent network Ionic Metallic Bonding in Solids The properHes of materials are a direct result of their structure and bonding characterisHcs 7 How are atoms arranged in solids? How are the atoms held together in solids? Structures of Solids: Crystalline: Amorphous: Bonding in Solids 8 Structure of Crystalline Solids Crystal LaXce: 3-D array of atoms Unit Cell: repeaHng unit of the crystal laXce 9 Bonding in Solids 1. Molecular solids Atoms or molecules held together by intermolecular forces ProperHes: so], low mp & bp What forces hold these molecules together in the solid state? Forces H2O LDF H-bonding Dipole-dipole LDF LDF LDF H-bonding Dipole-dipole LDF LDF Bonding in Solids 10 mp bp CO2 C3H8 C2H5OH Ar CCl4 Molecular solids Bonding in Solids 11 2. Network covalent solids Atoms or molecules held together in large networks (chains, planes, or 3-D) by covalent bonds ProperHes: hard, strong, stable High mp & bp What forces hold together the carbon atoms in solid diamond and graphite? Bonding in Solids 12 This is what the different allotropes of carbon look like Different structures = different properHes Allotropes of carbon Diamond Graphite Fullerene (C60) (fullerene with one side extended into a tube; variable lengths) Bonding in Solids 13 Carbon nanotube ProperHes of Allotropes of Carbon Diamond 4 bonds to each C sp3 hybridizaHon tetrahedral, dense Graphite (crystalline) 3 bonds to each C planar sp2 hybridizaHon delocalized -bonds van der waals forces between planes Uses Graphite: conducts current, soft: lubricant batteries (as electrode), pencils
Carbon Black (amorphous) tires, ink pigments, carbon paper Charcoal (amorphous) adsorb molecules in filters Coke (amorphous) reducing agent in metallurgical operation Uses Diamond: hardest substance known (Gem) abrasive, drill bits, cutting tools Bonding in Solids 14 Allotropes of Carbon Fullerenes MOLECULAR form e.g. C60 "Buckyballs" 3 bonds to each C sp2 hybridizaHon delocalized -bonds Nanotubes Sheets of graphite rolled up, capped by half of C60 molecule MulHwall or single walled Uses: nanoscale electronic circuits stronger than steel on nanoscale strong fibers with polymers Armchair (metallic behavior) Zigzag (diameter dictates semi- conductor or metallic behavior) Bonding in Solids 15 3. Ionic solids Atoms or molecules held together by ionic bonds Examples of Ionic Solids: NaBr, CaCO3, NH4Cl, FeCl2 In ionic crystals, ions pack themselves so as to maximize the aQracHons and minimize repulsions between the ions. Bonding in Solids 16 Bonding in Ionic Crystals Ferroelectric crystal: stores charge (becomes polarized in an electric field) Releases charge when struck by a photon Barium Oxygen Titanium Bonding in Solids 17 4. Metallic solids Atoms held together by metallict bonds "sea" of electrons model of metal bonding Can be used to explain some properHes of metals Electrical, thermal conducHvity Mechanical properHes: malleable and ducHle Bonding in Solids 18 Strength of metallic bond MelHng points of metallic solids vary a lot why? As strength of metallic bond increases, mp of metal increases. Cannot explain this trend using electron sea model of bonding in metals Bonding in Solids 19 Summary: Bonding in Solids MAIN GROUPS MAIN GROUPS 1A 1 1 7A 17 1 2A 2 4 3A 13 5 4A 14 6 5A 15 7 6A 16 8 8A 18 2 H
4.003 3 9 10 Li
20.180 11 12 13 14 15 16 17 18 Na
39.948 19 20 31 32 33 34 35 36 K
83.80 37 38 49 50 51 52 53 54 Rb
131.29 55 56 81 82 83 84 85 86 Cs
 87 88 114
 Atomic Molecular Network covalent Metallic Bonding in Solids 20 Bonding in Solids Elements 1. Metals: Metallic bonding 2. Semi metals: Network covalent solids B, Si, Ge, As, Sb, Te 3. Nonmetals Noble gases (Group 8): atomic solids Diatomics: molecular solids Group 7 (F2, Cl2, Br2, I2) and H2, N2, O2, Other non-metals S, P, Se molecular solids C : network covalent graphite, diamond, nanotubes Molecular fullerenes C60,C70, etc. Bonding in Solids 21 Classes of Solids Bonding in Solids 22 1. Which type of crystal will form when C6H6 (benzene) solidifies? 1. ionic 2. molecular 3. metallic 4. covalent-network 5. Amorphous Sample Problems 2. Indicate the type of crystal (molecular, metallic, covalent-network, or ionic) each of the following would form upon solidificaHon: 1. Zr 2. N2O4 3. SiO2 4. Ne 5. Ni(ClO3)2 3. For each of the following pairs of substances, predict which will have the higher melHng point. KBr Br2 SiO2 CO2 Ar Xe Bonding in Solids 23 ...
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