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Destroyer G Chem #42

Discussion in 'DAT Discussions' started by Quita3117, Jul 30, 2011.

  1. Quita3117

    5+ Year Member

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    Do all polar molecules have unshared electrons
     
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  3. radmazindds

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    I don't think so. As long as you have two bonded atoms with different electronegativities, you can have a polar molecule. In the wrong answer choices of this example, the atoms with high electronegativities are pulling on their respective central atoms equally/symmetrically(?), thereby canceling the polarity of the molecule.

     
  4. rmm30

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    that's a odd question. not sure what you mean. I don't think that shouldn't be used as criteria for discriminating polar from nonpolar. Think about all of the molecules you've encountered in your DAT study. 99% of them probably have unpaired electrons.

    Two methods i use to determine non polar:
    1) Is the shape of the molecule such that the poles cancel eother out. For example CCl4, ie tetrachlorocarbon. If you can imagine the molecule where all 4 Cl atoms are "hogging" electrons in their respective directions. Each bond is polar but the net polarity is 0 bc the vectors are cancelling each other out. A binary acid on the other hand (HF eg) will be polar.

    2) A good shortcut is to know your molecular geometry. If a molecule is linear, trigonal planar, tetrahedral, trig bipyramidal, or octahedral in both bonding AND molecular geometry then you have non-polar. All of these cases there are 0 lone pairs on the CENTRAL atom.

    for example BeCl2, BF3, CH4, PCl5, SF6 are all nonpolar. But H20 (Which has a tetrahedral bond angle geometry, but bent molecular geometry is polar)
     

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