The Bohr model is a relatively primitive model of the hydrogen atom, compared to the valence shell model. Not only did the Bohr model explain the reasons for the structure of the Rydberg formula, it also provided a justification for the fundamental physical constants that make up the formula's empirical results. While the Rydberg formula had been known experimentally, it did not gain a theoretical basis until the Bohr model was introduced. The model's key success lies in explaining the Rydberg formula for hydrogen's spectral emission lines. The improvement over the 1911 Rutherford model mainly concerned the new quantum mechanical interpretation introduced by Haas and Nicholson, but forsaking any attempt to explain radiation according to classical physics. In the history of atomic physics, it followed, and ultimately replaced, several earlier models, including Joseph Larmor's Solar System model (1897), Jean Perrin's model (1901), the cubical model (1902), Hantaro Nagaoka's Saturnian model (1904), the plum pudding model (1904), Arthur Haas's quantum model (1910), the Rutherford model (1911), and John William Nicholson's nuclear quantum model (1912). It is analogous to the structure of the Solar System, but with attraction provided by electrostatic force rather than gravity, and with the electron energies quantized (assuming only discrete values). In atomic physics, the Bohr model or Rutherford–Bohr model of the atom, presented by Niels Bohr and Ernest Rutherford in 1913, consists of a small, dense nucleus surrounded by orbiting electrons. The 3 → 2 transition depicted here produces the first line of the Balmer series, and for hydrogen ( Z = 1) it results in a photon of wavelength 656 nm (red light). The orbits in which the electron may travel are shown as grey circles their radius increases as n 2, where n is the principal quantum number. The Bohr model of the hydrogen atom ( Z = 1) or a hydrogen-like ion ( Z > 1), where the negatively charged electron confined to an atomic shell encircles a small, positively charged atomic nucleus and where an electron jumps between orbits, is accompanied by an emitted or absorbed amount of electromagnetic energy ( hν). Not to be confused with Bohr equation or Bohr effect.

Bohr model of oxygen atom