South Pasadena • AP Chemistry Name 10 ▪ States of Matter Period 10.1 LESSON – Date SOLIDS AND IMFS Types of Solids Example 1: For each of the following compounds, (1) determine the type of solid it forms, (2) identify the interparticle forces in the solid, and (3) sketch a sample unit cell for the solid. (a) Diamond, C (c) Calcium oxide, CaO Ca2+ O2− C C Network covalent Ionic solid, Ca2+ O2− C C solid, covalent bonds ionic bonds C (b) Copper, Cu Metallic solid, Metallic bonds (sea of electrons) O2− C C 2+ Cu2+ Cu2+ Cu Cu2+ (d) Sugar, C12H22O11 Molecular solid, IMFs (here, dipole-dipole) Ca2+ C12H22O11 C12H22O11 Cu2+ C12H22O11 C12H22O11 C12H22O11 Cu2+ O2− Ca2+ C C12H22O11 Cu2+ Cu2+ C12H22O11 C12H22O11 Which is expected to have the lowest melting point temperature? Why? Sugar (molecular solid) because it’s held by weak IMFs. (Sugar - 186°C, copper - 1085°C, CaO - 2572°C,diamond - 4727°C) Which is/are expected to conduct electricity? Why? Cu (metallic solid) as a solid; CaCl2 (ionic solid) as aqueous or molten. Summarize the four types of solids, how they are classified, and the inter-particle forces involved. Type Lattice Particle Inter-Particle Forces Metallic Solids Between metal atoms Metallic Bonds (sea of electrons) Ionic Solids Between cations/anions of ionic compounds Ionic Bonds Network Solids Between non-metal atoms (e.g. C, Si, SiO2) Covalent Bonds Molecular Solids Between molecules of covalent compounds Inter-molecular Forces (IMFs) Ionic Solids Example 2: Arrange the following solids from expected lowest to highest melting points: NaCl, MgO, BaO. k·q1·q2 Coulomb’s Law (F = d2 ) states that strength of attraction between charged species relate directly to electric charges and inversely to the square of the size. Here, melting points are NaCl (801°C) < BaO (1923°C) < MgO (2852°C). Na+/Cl− has the smallest charges, so NaCl has the lowest MP; since Ba2+ is larger than Mg2+, BaO has lower MP than MgO. Compare lattice energies – energy released when 1 mole of an ionic compound is formed from ions – NaCl (788 kJ/mol) < BaO (3029 kJ/mol) < MgO (3795 kJ/mol). Example 3: A sample of NaCl was hit, resulting in cleavage and brittleness. Draw a particulate representation of the crystal before and after the impact. Ionic solids form crystals of cations and anions held by strong ionic bonds, so they are hard. When they are hit, the oppositely charged ions are no longer aligned, and the repulsions between same-charged ions repel each other resulting in cleavage and brittleness. Metallic Solids and Alloys Example 4: List the general properties of metallic solids. How do electrons contribute to these properties? Electrical conductor because sea of electrons delocalized and free to move. Malleable and ductile because deforming the solid does not change the environment around the metal cation. Alloys are mixtures of a metallic solid with another element to modify the properties of the metallic solid. Type of Alloy Size of Elements Arrangement of Atoms Modified Properties Examples Atoms of the smaller element Rigidity of lattice increases, Interstitial Elements with fills the spaces between decreasing malleability and Steel (Fe + C) Alloy different radii. atoms of the larger element. ductility. Density is between that of the Substitutional Elements with Added element replaces two elements. Less malleable Brass (Cu + Zn) Alloy comparable radii. atoms of other element. and ductile than pure metal. Example 5: Draw a particulate representation of the steel and brass. Steel Brass O O Zn O Zn Zn Zn Zn Zn Zn O Zn Zn Zn Zn O Zn Zn Zn Zn O Zn Cu Zn Zn Zn O Zn Zn Zn Cu Cu Cu Zn Cu Zn Cu Cu Cu Cu Cu Cu Zn Cu Zn Cu Cu Cu Cu Zn Cu The surface of steel reacts with oxygen to form an inert oxide layer. Sketch the results of this process above. Network Covalent Solids Network covalent solids are usually of elements in the carbon family because they can form four bonds. Network solids typically have high (low/high) melting points because they are held by covalent bonds, and are rigid and hard because these bond angles are fixed. Graphite is an allotrope of carbon that form sheets of two-dimensional networks. Unlike other network covalent solids, graphite is soft (hard/soft) because the layers held by LDFs slide easily past each other. Silicon’s conductivity increases as the temperature increases. o Doping Si with a Family 15 element (e.g. P, As) creates an n-type semiconductor, in which the extra electron is allowed to conduct electricity. o Doping Si with a Family 13 element (e.g. B, Al, or Ga) creates a p-type semiconductor, in which movement of electrons into a positive hole conducts electricity. Molecular Solids and Inter-Molecular Forces Example 6: For each of the following compounds, (1) identify the type of inter-molecular force involved, and (2) sketch the interaction between two molecules. (a) He London dispersion forces (c) HCl Dipole-dipole interactions He (b) O2 H − Cl He London dispersion forces O=O O=O (d) HF H−F H − Cl Hydrogen bonding H−F Arrange the compounds from expected lowest to highest melting point temperature. He (−272°C) < O2 (−219°C) < HCl (−114) < HF (−84°) Summarize the three types of IMFs and the role of electrons involved in each one. London Dispersion Forces e− cloud polarized to form weak, induced dipole More e− = stronger LDF Strongest IMF in non-polar compounds Dipole-dipole Interactions Attraction between opposite poles of a polar compound Hydrogen bonding Strong dipole-dipole interactions in which H is pulled by small, high EN atoms (N, O, F).
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