Molecular Polarity

• A polar molecule is a covalent molecule that ends up having a and a side as a result of polar bonds and asymmetrical shape
• Recall that a polar bond is a covalent bond in which the bonding electron (e^-) pair is unequally shared between the bonding atoms. This unequal sharing is labeled using and
• Shapes of molecules are determined by knowing the number of bonding pair (bp) and number of lone pair (lp) around the central atom and using VSEPR theory. A lewis structure is usually drawn to help determine the number of lone pair (lp) and the number of bonding pair (bp).
• Asymmetrical shapes are:
  • Some linear molecules
  • Trigonal pyramidal
  • Bent, v-shape or angular
  • Any symmetrical molecular shape can be asymmetrical if the atoms attached to the central atom are not identical.
• Polar molecules are said to have a molecular dipole.

Molecular polarity is indicated by using an arrow on a structural representation of the molecule, the arrow head points in the direction of the negative side of the molecule. The tail of the arrow has a + sign attached to it.

Example:

• Evidence of molecular polarity is that polar substances are attracted to a charged rod whereas nonpolar substances are unaffected by a charged rod. Do you want to see it?
  

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