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Molecular Polarity - 2015.ppt
- 1.
- 2. Polar vs. Non-PolarMolecules Polarity in a molecules determines whether or not electrons in that molecule are shared equally. When determining the polarity of a molecule, it is all about symmetry. Asymmetric molecules tend to be polar. Symmetric molecules are always non- polar.
- 3. When determining thepolarity of a molecule, follow these steps: Draw the Electron Dot structure of the molecule. Using the electronegativity chart determine the difference in electronegativity for each bond. 0—0.5 = Non-polar Covalent Bond 0.6—1.9 = Polar Covalent Bond
- 4. The molecule isnon-polar if : each bond in the molecule is non-polar and there are no unbonded electron pairs. each bond in the molecule has the same polarity and there are no unbonded electron pairs on the central atom. There is no net dipole moment (all moments cancel out)
- 5. The molecule ispolar if: There is a net dipole moment each bond in the molecule is non-polar, but there are unbonded electron pairs on the central atom. bonds in the molecule have different polarities and/or there are unbonded electron pairs on the central atom.
- 6. Dipole Moment Direction ofthe polar bond in a molecule. Arrow points toward the more e-neg atom. H Cl + -
- 7. Polar molecules The effectof polar bonds on the polarity of the entire molecule depends on the molecule shape – water has two polar bonds and a bent shape; the highly electronegative oxygen pulls the e- away from H = very polar!
- 8. CHCl3 H Cl Cl Cl Determining MolecularPolarity Therefore, polar molecules have... – asymmetrical shape (lone pairs) or – asymmetrical atoms net dipole moment
- 9. Nonpolar Molecules Dipole momentsare symmetrical and cancel out. BF3 F F F B
- 10. Polar Bonds vs.Polar Molecules The effect of polar bonds on the polarity of the entire molecule depends on the molecule shape –carbon dioxide has two polar bonds, and is linear = nonpolar molecule!
- 11. Polar Molecules –Dipole momentsare asymmetrical and don’t cancel . –Molecule has a net dipole moment. net dipole moment H2O H H O
- 12. Determining Molecular Polarity Dependson: –dipole moments –molecular shape