1. Lecture 3111/18/05

2. Electron Pair Geometries Molecules with only single covalent bonds around central atom. Axial atomsEquatorial atoms

3. Repulsion Lone pair – Lone pair Lone pair – Bonding pair Bonding pair – Bonding pair Highest repulsion

4. Geometries for Four Electron Pairs

5. Molecular Geometries for Five Electron Pairs

6. Molecular Geometries for Six Electron Pairs

7. Example: What is the geometry of NH 3 ? 1. Draw Lewis structure 2. Determine # of bonds and lone pairs around central atom 3. Electron-pair geometry 4. Molecular geometry

8. Formaldehyde, CH 2 O CHH O C HH O 1. Draw Lewis structure 2. Determine # of bonds and lone pairs around central atom 3. Electron-pair geometry 4. Molecular geometry

9. Molecular polarity dependent on two things: Bond polarity Geometry Dipole Moment Measurement of the molecular polarity Molecular Polarity

10. CO 2 and H 2 O Which one is polar?

12. Intermolecular Forces (IMF) Noncovalent interactions Influence properties Melting point Boiling point Greater the IMF, higher the boiling point Solubility Like dissolves like Structure of complex molecules like proteins

13. Beta-carotene

14. Dipole-Dipole attraction Polar / Polar interaction More polar molecules  greater IMF 5 – 25 kJ/mol (150-1000 KJ/mol – covalent bond)

16. Polar molecules can induce a dipole in non-polar molecules Polarization Polarizability Degree to which electron cloud can be distorted to form dipole Higher the molar mass, greater the polarizibility Dipole / Induced Dipole Forces Polar / non-polar interaction