1. 1 Molecular Polarity

2. 2 Polar Molecules Polar molecules are molecules that have a slightly positive end or pole and a slightly negative end or pole. The molecule contains a dipole. Physical properties depend on the polarity of a molecule.

3. 3 Polarity of a Covalent Bond Electronegativity (EN) values are used to predict the polarity of covalent bonds. The greater  EN, the more polar will be the bond. A polar bond has a dipole or slight separation of charge (from the unequal sharing of bond electrons).

4. Polarity of a Molecule The polarity of a molecule depends on the sum of all the bond dipoles (individual dipoles or vectors). If there is a net dipole for the molecule, than the molecule is polar. A molecule that has polar bonds may or may not be polar.

5. Polarity of a Binary Molecule In binary molecules, the molecule polarity simply corresponds to the bond polarity.

6. Molecules with Non-polar Bonds For example, dihydrogen molecule (H 2 ) has a non-polar bond and thus is non-polar itself - the charge distribution is uniform across the molecule

7. Molecules with Polar Bonds On the other hand, hydrogen fluoride (HF) contains a polar bond and so it is a polar molecule. HF molecule has a concentration of negative charge (or greater electron density) near the fluoride (F) end of the molecule. The hydrogen end of the molecule has a concentration of a positive charge (or lower electron density). This reflects the fact that F atom is more electronegative than H atom.electronegative

8. 8    Molecular Geometry and Polarity.. H O + Net dipole    In molecules containing more than two atoms, the shape or geometry of the molecule impacts the polarity. Dipoles can cancel each other out resulting in nonpolar molecules. No Net dipole

9. 9 polar In general, a molecule is polar if: it is asymmetrical (isn’t a basic VSEPR shape) Ex: (polar) Ex: H 2 O, bent (polar) (polar) NH 3, pyramidal (polar) or if the terminal atoms/groups in a basic VSEPR shape differ. Ex: (polar) Ex: CH 2 C l 2, tetrahedral (polar) Molecular Geometry and Polarity

10. 10 Symmetrical Molecules Molecules that exhibit symmetry in the distribution of electrons would have no net dipole. These molecules are considered non polar. Non polar VSEPR shape identical atoms

11. 11 Symmetrical Molecules

12. Asymmetrical Molecules Molecules that exhibit asymmetry in the distribution of electrons will result in a net dipole. These molecules are considered polar.

13. Asymmetrical Molecules

14. Let’s Review