Rutherford's atomic model was complemented by a new concept introduced by Danish physicist Niels Bohr:
"The electron describes a circular orbit around the nucleus without gaining or losing energy."
Each orbit described by the electron is called the energy level or energy layer. In an atom, there are several circular orbits, each with a certain energy value.
Other later models specify the characteristics of the orbits or layers of energy, incorporating the discussion of electron considered as particle and / or wave.
More recent research after the elaboration of the Rutherford-Böhr model has shown that it is impossible to determine at once the position and velocity of an electron. So scientists say the electrons are likely to be in one or another region of the electrosphere.