Question

Why can only electrons move and get transferred? Why not protons?

Answer 1

Electrons are not affected by the strong force, and so they only get trapped by the electrical attraction to the nucleus which is much weaker in ionized atoms. Therefore it is easier for electrons to move away from one atom to another, transferring charge.
Protons interact in ways that electrons do not. They get trapped inside nuclei due to the effects of the strong force. Electrons are not affected by the strong force, and so they only get trapped by the electrical attraction to the nucleus which is much weaker in ionized atoms. Therefore it is easier for electrons to move away from one atom to another, transferring charge