Outline for Today. Monday, Nov. 26. Chapter 11: Intermolecular Forces and Liquids. Intermolecular Foces. Comparing States of Matter

Transcription

1 Outline for Today Monday, Nov. 26 Chapter 11: Intermolecular Forces and Liquids Intermolecular Foces Comparing States of Matter Properties of Liquids Phase Changes!1

2 Exam 3 Reminders When: Wednesday at 5pm Where: First floor of Keyes What: Cumulative with a focus on chapters 6 through 9 Review Session Tonight 7-9pm Keyes 105

3 Chapter 6: Electronic Structure of Atoms There are 4 equations related to the wave behavior of light and matter, know when and how to use them! Know the rules for the quantum numbers and how they relate to orbital shapes and number of nodes. Be able to write electron configurations for all elements. Don t forget: there are 4 exceptions to the electronic configuration patterns (Cr, Cu, Ag, Au)

4 Chapter 7: Periodic Trends There are 4 periodic trends we discussed. ZEff, sizes of atoms and ions, ionization energy, and electron affinity. You should know the definitions, trends, and reasons why each trend occurs. You should be able to rationalize exceptions based on electron configurations.

5 Chapter 8: Chemical Bonding Identify Ionic Bonding and Lattice Energy Lewis Structures Formal Charge Bond Polarity and Trends in Electronegativity Resonance structures and exceptions to the octet rule Calculations using Bond Enthalpy

6 Chapter 9: Molecular Geometry and Bonding Theories Three dimensional molecular shapes (Tables 9.1 through 9.4) Orbital Hybridization and Multiple bonds Molecular Polarity (REALLY IMPORTANT for Chapter 11!) Molecular orbital theory for 1st and 2nd row diatomic (figure 9.43) Bond Order and Paramagnetic/Diamagnetic

7 A Brief Review of Polarity and Dipole Moments Draw a Lewis Structure of CF2I2. Is it Polar or Nonpolar?

8 Chapter 11: Intermolecular Forces and Condensed Phases (Liquids and Solids)

9 The waxy molecules coating the lotus leaf are different than the water! They are Hydrophobic! Why? Why does the water droplet bead up on the lotus leaf? Why doesn t it spread out? Intermolecular Forces! (The waxy lotus leaves lack hydrogen bonding!)

10 Intermolecular Forces are the Forces of INTERACTING Molecules Weakly Interacting. Weak Intermolecular Forces Cl2 Br2 I2 Gas Liquid Solid Strongly Interacting. Strong Intermolecular Forces

11 Intermolecular Forces Intermolecular Forces= The attractive forces between molecules

12 Intermolecular Forces London Dispersion: Attraction between momentary or instantaneous dipoles in molecules. Generally Weaker Dipole-Dipole: Attraction between partial charges due to permanent dipoles Hydrogen-Bonding: Attraction between partial charges on H-F, H-O, or H-N bonds. Ion-Dipole: Attraction between ions and partial charges of dipoles Generally Stronger

13 Intermolecular Forces London Dispersion: Attraction between momentary or instantaneous dipoles in molecules. Dipole-Dipole: Attraction between partial charges due to permanent dipoles Hydrogen-Bonding: Attraction between partial charges on H-F, H-O, or H-N bonds. Ion-Dipole: Attraction between ions and partial charges of dipoles Which Molecules? All Molecules Polar Molecules Needs H attached to O, N, or F Needs an Ion van der Waals forces

14 London Dispersion

15 Strength of London Dispersion Forces depends on Polarizability Polarizability: How easy it is to alter the electron density of a molecule (how sloshy the electrons is) Polarizability tends to increase with the number of electrons (roughly molecular weight). Example: Order the following molecules from most polarizable to least: F2, I2, Cl2 SnH4, SiH4, CH4

16 Stronger the Intermolecular Force, the Higher the Boiling Point Temperature! Example: Sort the following by increasing Boiling Point Temperature H2Te, H2S, H2Se

17 London-Dispersion Depends on Shape Same Molecular Weight, Different Shapes Different Boiling Points

18 Dipole-Dipole Dipole-Dipole: Attraction between partial charges due to permanent dipoles. Example: Is there a dipole on CH3CN? How do the dipoles interact?

19 Dipole-Dipole Interactions in Solids

20 Dipole Dipole Interactions in Liquids

21 The larger the dipole, the stronger the dipole-dipole interactions! O O N Increasing Polarity Increasing Dipole-Dipole Interactions Increasing Boiling Point

22 Hydrogen-Bonding is a special type of dipole interaction Hydrogen-Bonding: Attraction between partial charges on H-F, H-O, or H-N bonds. H-F, H-N, and H-O are especially polar bonds! They interact strongly with small electronegative ions or atoms (like F, O, or N of another molecule). That interaction is called hydrogen bonding.

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24 NOT A Hydrogen Bond H H H C H H C H H H Yes, there are hydrogens bonded to stuff, but there is no intermolecular hydrogen bonding interaction. There is no hydrogen bond.

25 Hydrogen Bonding Is Critical for Understanding the Properties of Water!

26 Predict the relative strengths of the dipole-dipole interactions Order the following by increasing boiling point (based on strength of the intermolecular interactions) O O a) Butane b) Propyl alcohol c) 2-Methylpropane d) Isopropyl alcohol

27 Intermolecular Forces with Charged Particles Ion-Dipole Forces: Attraction (or Repulsion) between an ion and the partial charge on the end of a molecule

28 Try this chart with: Ammonia, Methane, Acetic Acid, Hydrochloric Acid