Although the atomic model of Rutherford was certainly ingenious, it did not take into consideration the principle of classical physics, according to which “A charged particle loses energy continuously during movement”: according to this principle the electron would have to lose more and more energy by approaching its orbiting more and more to the nucleus to hit it and thus to destroy the destruction of matter, which is obviously not acceptable.

The Danish physicist Niels Bohr took charge of solving this problem and, after working for some time with Thompson and later with Rutherford, suggested that “the electrons cannot stay at random distances but only defined according to certain amounts of energy, or energy levels. ”

This intuition posed a fascinating image of the electrons, which therefore would have always had to traverse circular trajectories, called stationary orbits. Despite all this atomic model did not present any experimental proof until, examining the spectrum of the hydrogen Bohr realized that this phenomenon was in accordance with its experimental model, and that could provide a clear experimental proof: how can we otherwise think that does hydrogen gas, if appropriately excited, give rise to a continuous spectrum but to a striped spectrum?

According to Bohr’s model when, due to an electric discharge or heat, the electrons in the hydrogen acquire energy, they would be able to move in the course of their trajectory and move to a subsequent level of energy, then return to their fundamental state by returning the energy acquired in the form of light energy, in the case of hydrogen, red for the first energy jump, blue-green for the second and finally violet for the third.

(You can see a scheme of the Bohr’s atomic model here.)

Further studies on the spectrum of the elements revealed that each element has a characteristic striped spectrum, which could be compared to a sort of “fingerprint” of the element.

Summarizing, we can summarize Bohr’s atomic model in this way:

– The atom consists of a nucleus where protons and neutrons are found

– The electrons rotate around the nucleus describing certain circular orbits, called stationary orbits

– As long as the electrons rotate in their orbit, they neither acquire nor lose energy

– The orbits are quantized, that is they are clearly separated, and their distance from the nucleus is a function of the energy associated with them

– If appropriately excited, an electron can pass from one orbit to another higher energy level, assuming greater amounts of energy, equal to the difference in energy between the two orbits.

– The electron, returning to the fundamental state, returns the energy acquired in the form of light that appears in the spectrum as a colored line.