Why only electron can transfer from one body to another body in frictional electrics ?

A glass rod rubbed with silk is used to charge a gold leaf electroscope and the leaves are observed to diverge. The electroscope thus charged is exposed to $X$-rays for a short period. Then

A body can be negatively charged by

Why can we say that charge of any body is always an integral multiple of $'e'$ ?

Write the activity to make simple electroscope.

What is the meaning of addition of charges ?