What is called quantization of electric charge? Write the $SI$ unit of electric charge.

(N/A) Quantization of electric charge is the property by virtue of which all free charges are integral multiples of a basic unit of charge denoted by $e$. Thus,charge $q$ on a body is always given by $q = n \cdot e$,where $n$ is an integer $(n = 0, \pm 1, \pm 2, \dots)$ and $e \approx 1.602 \times 10^{-19} \ C$. The $SI$ unit of electric charge is the Coulomb $(C)$.