1. IX. 3. Molecular Polarity p. 198-204

3. Polar Molecules The bond between atoms with different electronegativities gives rise to a dipole Dipole-dipole bonds are stronger than London Forces

4. Ex: H-Cl Has dipoles Unbalanced/ asymmetrical Dipole-dipole bond between molecules Polar molecule

5. Ex: Cl-Cl no dipoles Balanced molecule only London forces present between molecules Non-polar molecule

6. Other examples: H 2 O BI 3 O 2 CCl 4 CCl 3 H

7. Boiling & Melting Temperature Ionic highest bp & mp Then if covalent: Polar molecule with a H-bond Polar molecule Higher # of electrons (atomic #)

8. Ex: N 2 (l) = - 196 C Covalent Non-polar Low mp & bp

9. O 2 (l) = - 183 C Covalent Non-polar More electrons than N

10. NO (l) = - 152 C Polar covalent So higher mp & bp than non-polar covalents