Want to stay on top of all the space news? Follow @universetoday on TwitterThe Bohr Model is the simplest modern depiction of the atom. According to this model the atom, electrons orbit the nucleus at set distances. When an electron changes orbits, it does so in a sudden quantum leap. The energy difference between the initial and final orbit is emitted by the atom in bundles of electromagnetic radiation called photons. This model was developed by Niels Bohr. Since the Bohr atomic model is a quantum physics-based modification of the Rutherford model of 1911, many sources combine the two, referring to the Rutherford–Bohr model.
Bohr’s atomic model was introduced in 1913. The model’s key success lay in explaining the Rydberg formula( used in atomic physics to describe the wavelengths of spectral lines of many chemical elements. The Rydberg formula was not truly accepted until the Bohr model’s introduction because the Bohr model explained the reason for the structure of the Rydberg formula, it also provided a justification for its empirical results in terms of fundamental physical constants. Today the Bohr model is obsolete, but it is still taught as a way to introduce students to quantum mechanics.
The Bohr atomic theory improved upon the Rutherford theory in a few key ways. Rutherford supposed that the electrons revolved in a way similar to a planet around the sun. It also supposed that electrons all gave off electromagnetic energy. Based on this, electron would eventually lose all of their energy and collapse onto the nucleus, making all atoms unstable. The Bohr model showed that atoms were stable and electrons only followed certain motions. This was proven with experiments showing that electrons emitted light at certain, constant frequencies.
Over the years there were many improvements made to the Bohr atom. The best known of them was the Bohr-Summerfield model. This revised model suggested that electrons travel in elliptical orbits around a nucleus instead of the Bohr model’s circular orbits. This model supplemented the quantized angular momentum condition of the Bohr model with an additional radial quantization condition.
The Bohr model was a step towards what is now the study of quantum mechanics. This link takes you to a good article about the Bohr model. Here on Universe Today we have a great article about several different atomic models. Astronomy Cast offers a good episode about a tough area of quantum mechanics called entanglement.