One of the mysteries of the atom is that the electron and the nucleus attract each other. This attraction is called electrostatic force, the force that holds the electron in orbit. This force may be illustrated with lines as shown in Figure 3.

Figure 3 Electrostatic Force

Without this electrostatic force, the electron, which is traveling at high speed, could not stay in its orbit. Bodies that attract each other in this way are called charged bodies. As mentioned previously, the electron has a negative charge, and the nucleus (due to the proton) has a positive charge.