Question

Which of the following contains (electrovalent) and polar (covalent) bond
A) $C{H_4}$
B) ${H_2}{O_2}$
C) $N{H_4}Cl$
D) $HCN$

Answer 1

A covalent bond is formed when two atoms share electrons. The key distinction between an electrovalent and a covalent bond is that an electrovalent bond is formed when two atoms are attracted to each other electrostatically, while a covalent bond is formed when two atoms exchange electrons.

Complete answer:

1. The $N - H$ bond in $N{H_4}Cl$ is polar due to a significant electronegativity difference between $N(3.0)$ and $H(2.1)$ .
2. The $H - C$ and $C - N$ bonds in $HCN$ are polar due to the electronegativity difference between $C(2.5)$ and $N(3.0)$ for the $H - C$ bond and $C(2.5)$ and $H(2.1)$ for the $C - N$ bond.
3. Because of the electronegativity difference between $O(3.5)$ and $H(1.5)$ , the $O - H$ bond in ${H_2}{O_2}$ is polar $(2.1)$ . The $O - O$ bond, on the other hand, is non-polar.
4. The $C - H$ bonds in $C{H_4}$ are also polar.
   Hence, the correct option is (C) $N{H_4}Cl$ .

Note:
When two nonmetal atoms share a pair of electrons, they form a covalent bond. The electrons present are in the atoms' outer shells. Covalent bonds are very strong and take a lot of energy to crack so both nuclei are highly attracted to the shared pair of electrons.