1. Polar Bonds and Molecules Chapter 8.4

2. If the difference in electronegativity is between
1.7 to 4.0: Ionic Bond
0.3 to 1.7: Polar Covalent Bond
0.0 to 0.3: Non-Polar Covalent Bond

3. Electronegativity Scale

4. Polar Covalent Bond vs Non-Polar Covalent Bond

5. Polar Covalent vs Non-Polar Covalent

6. Drawing Polar Bonds and Molecules

7. Net Dipole of Molecules
Dipole – separation of charges within a molecule between two covalently bonded atoms.
Net Dipole – When all the dipole vectors are summed to give one overall dipole.

8. Attractions Between Molecules or Intermolecular Forces (IM Forces)

9. We have already talked about intramolecular forces.
Intramolecular forces hold atoms together in a molecule.
Covalent bonds would be an example.
Intermolecular forces are attractive forces between molecules.

10. Intermolecular Forces
Intramolecular = strong
Intermolecular = weak
They do control physical properties such as boiling and melting points, vapor pressure, and viscosity

11. Types of Intermolecular Forces
van der Waals Forces
Dipole-dipole interactions
Ion-Dipole interactions
London dispersion forces

12. Dipole-Dipole Interactions
Molecules that have permanent dipoles are attracted to each other.

13. Ion-Dipole Interactions
Attractive forces between an ion and a polar molecule
Ion-Dipole Interaction
The larger the charge the stronger the force

14. London Dispersion Forces
Occasionally electrons wind up on the same side of the atom.

15. London Dispersion Forces
At that instant, the helium atom is polar.

16. London Dispersion Forces
This polar helium atom then induces a dipole
on a neighboring helium atom.

17. London Dispersion Forces
London dispersion forces, or dispersion forces, are attractions between an instantaneous dipole and an induced dipole.

18. London Dispersion Forces
These forces are present in all molecules, whether they are polar or nonpolar.
The tendency of an electron cloud to distort in this way is called polarizability.

19. Types of Intermolecular Forces
Hydrogen Bonding
The dipole-dipole interactions experienced when H is bonded to N, O, or F are unusually strong.
We call these interactions hydrogen bonds.

20. Hydrogen Bonding: Water

21. Hydrogen Bonding: Water