Question

Define polar and nonpolar molecules. Give examples.

Answer 1

Hint: There is charge separation which exists due to the repulsive forces between the particles of the same nature. This is called polarity. Polarity leads to the formation of dipole moments of the molecules and ions.

Complete step by step solution:
-Based on polarity, the molecules can be divided into 2 parts- polar and nonpolar molecules. Polar molecules are those which have a net dipole moment due to the differences in the electronegativities of the atoms present in the molecule which do not allow to cancel the dipoles.
Non-polar molecules are those which have net dipole moment as zero as the dipoles of the atoms are cancelled out within the molecule.
-Polarity is important to study as it defines several physical properties of the molecule like melting point, boiling point, dipole moment, solubility. It is governed by the principle of electronegativity. Different atoms have different electronegativities which causes the attraction of shared electron pairs towards themselves by different amounts.
-Atoms like F,O,N have a large amount of electronegativity and they pull the electrons towards themselves. This leads to uneven charge distribution thus leading to polarity.
-Non-polar bonds are formed generally when the difference in the electronegativities of atoms is less than 0.5 and polar bonds are formed when the difference is more than 0.5
-Polar bonds have a net dipole moment and they generally are formed when there is no symmetry present within the molecule. With no symmetry, the dipole moments of different atoms do not cancel out each other thus leading to a net dipole moment.
-Non-polar bonds do not have any net dipole moment and are generally formed in the compounds where there is a presence of symmetry. Even if the atoms have a net dipole moment, the overall dipole moment of the compound is zero because they cancel each other.
-Some examples of polar molecules are $HF,HCl,H_{2}O,N{H}_3$
The orientation of the dipole moment can be shown as $H\to Cl,H\to F$
Some examples of non-polar molecules which are caused due to symmetry are $CC{l}_4,C{H}_{3}C{H}_{2}C{H}_3,C{O}_2,O_2$.

Note: Lone pairs play an important part in deciding the symmetry of a molecule and thus in determining if the molecule is polar or nonpolar. Also when we deal with the geometrical isomers, then we need to keep in mind that in some compounds where symmetry occurs, cis form has a dipole moment and trans form has ney dipole zero.