Editing Bohr model (section)

===Atomic spectra===
By the early twentieth century, it was expected that the atom would account for the many atomic spectral lines. These lines were summarized in empirical formula by [[Balmer formula|Johann Balmer]] and [[Rydberg formula|Johannes Rydberg]]. In 1897, Lord Rayleigh showed that vibrations of electrical systems predicted spectral lines that depend on the square of the vibrational frequency, contradicting the empirical formula which depended directly on the frequency.<ref name=KraghQuantumAtom2012>{{Cite book |last=Kragh |first=Helge |title=Niels Bohr and the Quantum Atom: The Bohr Model of Atomic Structure 1913–1925 |date=2012 |publisher=Oxford University Press |isbn=978-0-19-163046-0}}</ref>{{rp|18|q=By the early twentieth century it was desirable for a candidate theory of atomic structure to account for line spectra and their regularities, but in fact none of the models available at the time were able to do so.}}<ref>{{Cite journal |last=Rayleigh |first=Lord |date=January 1906 |title=VII. On electrical vibrations and the constitution of the atom |url=https://zenodo.org/record/1837403 |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science |volume=11 |issue=61 |pages=117–123 |doi=10.1080/14786440609463428}}</ref>
In 1907 [[Arthur W. Conway]] showed that, rather than the entire atom vibrating, vibrations of only one of the electrons in the system described by Thomson might be sufficient to account for spectral series.<ref name="Whittaker">{{Cite book |last=Whittaker |first=Edmund T. |title=A history of the theories of aether & electricity. 2: The modern theories, 1900 - 1926 |date=1989 |publisher=Dover Publ |isbn=978-0-486-26126-3 |edition=Repr |location=New York}}</ref>{{rp|II:106}} Although Bohr's model would also rely on just the electron to explain the spectrum, he did not assume an electrodynamical model for the atom.

The other important advance in the understanding of atomic spectra was the [[Rydberg–Ritz combination principle]] which related atomic spectral line frequencies to differences between 'terms', special frequencies characteristic of each element.<ref name=PaisInwardBound/>{{rp|173|q=Ritz's principle was absolutely crucial to Bohr in his formulation of the quantum theory of spectra.}} Bohr would recognize the terms as energy levels of the atom divided by the Planck constant, leading to the modern view that the spectral lines result from energy differences.<ref name=Bohr1925>{{Cite journal |last=Bohr |first=N. |date=December 1925 |title=Atomic Theory and Mechanics1 |url=https://www.nature.com/articles/116845a0 |journal=Nature |language=en |volume=116 |issue=2927 |pages=845–852 |doi=10.1038/116845a0 |bibcode=1925Natur.116..845B |issn=0028-0836|url-access=subscription }}</ref>{{rp|847}}<ref name=Perovic2021>{{Cite book |last=Perović |first=Slobodan |title=From data to quanta: Niels Bohr's vision of physics |date=2021 |publisher=The University of Chicago press |isbn=978-0-226-79833-2 |location=Chicago London |chapter= Spectral Lines, Quantum States, and a Master Model of the Atom}}</ref><!-- Both Conway and Ritz discussed -->