Who represented the quantization of electric charge first and on what basis?

We have three identical metallic spheres $A, B$ and $C$. $A$ is given a charge $Q$,and $B$ and $C$ are uncharged. The following processes of touching of two spheres are carried out in succession. Each process is carried out with sufficient time.
$(i)$ $A$ and $B$
$(ii)$ $B$ and $C$
$(iii)$ $C$ and $A$
$(iv)$ $A$ and $B$
$(v)$ $B$ and $C$
The final charges on the spheres are

$A$ solid sphere of mass $1 \ gm$ contains $5 \times 10^{21}$ atoms. If one electron is removed from every $0.01\%$ of the atoms,what is the charge acquired by the sphere in $C$?

What is the total charge of the electrons in a neutral atom?

The fact that electric charges are integral multiples of the fundamental electronic charge was proved experimentally by

Which of the following electric charges is not possible?