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Chemistry

Polar vs. Non-polar Molecules. Chemistry. Molecular Polarity. Just like bonds can be polar because of un-equal electron distribution, molecules can be polar because of un-equal electron cloud distributions These imbalances are not the same as ion formation.

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Chemistry

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  1. Polar vs. Non-polar Molecules Chemistry

  2. Molecular Polarity • Just like bonds can be polar because of un-equal electron distribution, molecules can be polar because of un-equal electron cloud distributions • These imbalances are not the same as ion formation. • How do we know when a molecule is polar?

  3. Molecular Polarity • 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.

  4. When determining the polarity 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—0.4 = Non-polar 0.5—1.7 = Polar • The molecule is non-polar or polar based on the following criteria:

  5. The molecule is non-polar if either: • each bond in the molecule is non-polar and there are no un-bonded electron pairs on the center atom. (example: CBr4) • Each C-Br bond is non-polar (ΔEN=0.3), no side of the molecule has more electron density. It is symmetrical! • each bond in the molecule has the samepolarity and there are no un-bonded electron pairs on the central atom. (Example: CF4) • C-F bond is polar ΔEN=1.5, • But, Molecule is symmetrical

  6. The molecule is polar if: d+ • each bond in the molecule is non-polar, but there are un-bonded electron pairs on the central atom. Example: NBr3 • bonds in the molecule have different polarities and/or there are un-bonded electron pairs on the central atom. Example: CH3Br d- d- d+

  7. Molecular Polarity Summary

  8. Molecule Polarity The H─Cl bond is polar. The bonding electrons are pulled toward the Cl end of the molecule. The net result is a polar molecule.

  9. Molecule Polarity The H─O bond is polar. Both sets of bonding electrons are pulled toward the O end of the molecule. The net result is a polar molecule.

  10. Molecule Polarity The O─C bond is polar. The bonding electrons are pulled equally toward both O ends of the molecule. The net result is a nonpolar molecule. COS is linear. C and S have the same EN (2.0) but the sulfur atom is bigger than the oxygen side (more electron density),so the molecule is polar overall.

  11. SO2 PF3 BCl3 BHF2 Polar (unbonded e- on center atom!) Polar (unbonded e- on center atom!) Non Polar (bonds are polar, but symmetrical) Polar – different bond polarities Polar or Non-Polar?

  12. More Molecular Polarity… • Molecular 3D Models website

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