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

Hint: 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.