The negative charge of the electron has exactly the same magnitude as the positive charge of the proton. If one or more electrons are removed from the neutral atoms, the remaining positively charged particlesare called positive ions. A negative ion is an atom that has gained one or more electrons.
Picture of an atom
It is clear that usually the negative charge is transferred when two bodies are rubbed together. The electrons that are less tightly bound tend to move from its atom to the other. The number of electrons that are transferred will be insignificant compared to the total number of electrons or protons in the body. Thus the charge acquired by friction is a very small fraction of the total positive and negative charge content in a body .
Some substances which allow electricity to pass through them are called Conductors while others that do not let electricity pass are called Insulators. In conductors, the outer electrons of individual atoms get detached and move almost freely inside the substance, where as in insulators, there are no free electrons. It is because of these free electrons that a conductor allows charges to pass through them .Example of conductor:
Connect a charged plastic rod to an uncharged pith ball through a copper wire. Instantly the ball gets charged.
