Chemistry

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Polar vs. Non-polar Molecules

• Chemistry

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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?

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Molecular Polarity

• Polarity in a molecules determines whether or not
  electrons in that molecule are distributed
  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.

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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.
• 00.4 Non-polar 0.51.7 Polar
• The molecule is non-polar or polar based on the
  following criteria

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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 (?EN0.3), no side of
  the molecule has more electron density. It is
  symmetrical!
• each bond in the molecule has the same polarity
  and there are no un-bonded electron pairs on the
  central atom. (Example CF4)
• C-F bond is polar ?EN1.5,
• But, Molecule is symmetrical

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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
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Molecular Polarity Summary
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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.
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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.
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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.
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Polar or Non-Polar?

• Polar (unbonded e- on center atom!)
• Polar (unbonded e- on center atom!)
• Non Polar (bonds are polar, but symmetrical)
• Polar different bond polarities

• SO2
• PF3
• BCl3
• BHF2

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More Molecular Polarity

• Molecular 3D Models website