Question

Define polar and nonpolar molecules? Give examples.

Answer 1

Polar molecules have asymmetric distribution of charges along the molecules while the non-polar molecules have a symmetric distribution of charges. The polarity or the non-polarity of the molecules depend on the individual bond moment of the molecules.

Complete answer:
Now, there are molecules in which there are atoms that are separated from each other having equal charges due to the difference of electronegativities between the atoms but the arrangement of the atoms in the molecules is such that the bond moments cancel each other and the net bond moment becomes zero. These molecules are called non-polar molecules. An example of this is carbon dioxide in which the carbon and the oxygen atoms have electronegativity differences but due to the arrangement of the two carbon oxygen bonds in the exactly opposite directions, the bond moment is zero and the molecule becomes non-polar. Polar molecules are those in which the atoms of the molecules are arranged in such a way that there exists a net bond moment and the molecule has polarity.

Note:
The dipole moment is a physical vector quantity which depends on the charge separation between the atoms in a molecule. It is defined as the product of the charge on the atoms of the molecules and the distance between them which is basically the bond length of the molecule. It is mathematically expressed as:
Dipole moment $\left( \text{ }\mu\text{ } \right)$ = charge on the atoms $\left( \text{q} \right)$ x distance between the atoms in the molecules $\left( \text{d} \right)$