Question

Which of the following molecules possesses polar and nonpolar covalent bonds?
A. \[\text{N}{{\text{H}}_{\text{4}}}\text{Cl}\]
B. $\text{CC}{{\text{l}}_{4}}$
C. ${{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}$
D. $\text{HCN}$

Answer 1

Hint: The bond shared between any two atoms is largely dependent on the nature of the atoms and their electronegativities. This is what decides a covalent bond will be polar or nonpolar.

Complete answer:
> In the \[\text{N}{{\text{H}}_{\text{4}}}\text{Cl}\] molecule the bonds between nitrogen and hydrogen are polar covalent in nature due to the electronegativity differences between the atoms, the lone pair on the nitrogen atom is donated to a hydrogen ion leading to the formation of the coordinate covalent bond. Finally, the ammonium ion forms an ionic bond with the chloride ion.
> In $\text{CC}{{\text{l}}_{4}}$, the bonds shared by the carbon and chlorine atoms is polar covalent in nature but as the bond moments of the carbon and chlorine bonds are placed exactly opposite to each other in the molecule so they cancel each other and the molecule becomes non-polar.
> In ${{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}$ each oxygen atom is bonded to another oxygen atom and a hydrogen atom. The bond between the oxygen atoms is non-polar covalent in nature due equal sharing of electrons while that between hydrogen and oxygen is polar-covalent due to the difference in electronegativities of the atoms.
> In $\text{HCN}$, all the bonds between hydrogen, carbon, and nitrogen are polar covalent in nature due to the difference in electronegativities between the atoms.

Hence, the correct answer is option C.

Note: When two atoms share their valence shell electrons to complete their octet and gain stability, then that bond is called “Covalent Bond”. The covalent bond can be either polar or nonpolar depending on the atoms that form the bond. As for example consider the bond between the hydrogen atoms in a ${{\text{H}}_{2}}$ molecule, it is a nonpolar covalent bond because the electron pair is equally shared between both the atoms.