Nucleus is present in the center of Atom. It contains protons and neutrons. Protons carry positive charge and neutrons carry negative charge. The protons and neutrons in an atom are equal. So atom as a whole is neutral. Around the nucleus, there are negatively charged electrons revolving in different orbits.
Protons and neutrons are held together by strong nuclear forces, but the electrons are less tightly bound. When two bodies are rubbed with each other then electrons are transferred to that body whose work function is low. The body which loses electrons is charged positively due to the loss of negative charge i.e. Electrons. On the other hand the body that gains electrons gets negative charge.
