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Bonding What exactly is a bond? Depends…Ionic or Covalent ? Polar?

Bonding What exactly is a bond? Depends…Ionic or Covalent ? Polar?. NON-POLAR COVALENT=> equal sharing of electron pair 0 < ∆EN < 0.4 POLAR COVALENT= unequal sharing of electron pairs , e-’s spend more time closer to one atom, 0.4 < ∆EN < 1.7

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Bonding What exactly is a bond? Depends…Ionic or Covalent ? Polar?

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  1. Bonding What exactly is a bond? Depends…Ionic or Covalent? Polar? NON-POLAR COVALENT=> equal sharingof electron pair 0 < ∆EN < 0.4 POLAR COVALENT= unequal sharing of electron pairs, e-’s spend more time closer to one atom, 0.4 < ∆EN < 1.7 IONIC “BOND”= transfer of electrons, no physical connection to one another, atoms are held together by an electrostatic attraction, ∆EN > 1.7

  2. Molecular Polarity • Tutorial 1: p. 226 • Figure 6: p. 228 • p. 227 #1,2 • HW: p. 229 #1-7ab No molecular dipole => non-polar molecule Molecular Dipole is present => polar molecule No molecular dipole => non-polar molecule Molecular Dipole is present => polar molecule

  3. Which process requires more energy?Why? H2O(l) H2O(g) or 2 H2O(l) 2 H2(g) + O2(g)

  4. Intermolecular Forces • London force (dispersion) • due to electrostatic attraction b/w protons in one molecule and electrons of neighbouring molecules • strength α # of e- Cl2bp = -35°C I2bp = 84°C Explain the trend in bp. Cl2 has 34 e-. I2 has 106 e-. I2 has more e- => greater LDF => higher bp

  5. Intermolecular Forces • dipole-dipole force • due to attraction of one dipole by surrounding dipoles • strength α molecular polarity CH2O is a polar molecule => has a dipole force, LDF (16 e-) C2H6 is a non-polar molecule => no dipole force, only LDF (18 e-) CH2O has higher bp due to dipole-dipole force CH2O bp = -21°C C2H6bp = -89°C Explain the trend in bp. Include diagrams to support your explanation.

  6. Predict which substance has the stronger dipole force: HCl or HBr HCl is the more polar molecule (ΔEN is greater) => stronger dipole forces (Draw diagrams to support your explanation.)

  7. Intermolecular Forces • Hydrogen bonding • due to attraction of a H bonded to a highly EN atom (O, N or F) in one molecule by the lone pair of e- on a highly electronegative atom of a neighbouring molecule H2Te bp = -10°C H2Se bp = -50°C H2S bp = -80°C H2O bp = 100°C Explain the trend in bp.

  8. Identify the type of IMF Strongest? Intermolecular Forces

  9. Properties of Liquids Cohesiveforces: • attractions b/w like molecules Adhesive forces: • attractions b/w unlike molecules

  10. Capillary Action • Water is transported in thin tubes from roots to shoots. • adhesive forces (b/w H2O and sides of tubes) and cohesive forces (b/w H2O molecules) • Water is pulled up against gravity!

  11. Intermolecular Forces and Properties • Boiling and melting pt • Surface tension • Meniscus shape • Capillary action • Volatility • Viscosity • Solubility • Wetting Action • Hydrophobicity

  12. Why is glycerol more viscous than water?

  13. Homework • Section 4.7 • p. 244 #1,2 • p. 247 #1-6

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