Editing Bohr model (section)

=== Nicholson atom theory ===
In 1911 [[John William Nicholson]] published a model of the atom  which would influence Bohr's model. Nicholson developed his model based on the analysis of astrophysical spectroscopy. He connected the observed spectral line frequencies with the orbits of electrons in his atoms. The connection he adopted associated the atomic electron orbital angular momentum with the Planck constant.
Whereas Planck focused on a quantum of energy, Nicholson's angular momentum quantum relates to orbital frequency.
This new concept gave Planck constant an atomic meaning for the first time.<ref name="McCormmach1966">{{Cite journal |last=McCormmach |first=Russell |date=1 January 1966 |title=The atomic theory of John William Nicholson |journal=Archive for History of Exact Sciences |volume=3 |issue=2 |pages=160–184 |doi=10.1007/BF00357268 |jstor=41133258 |s2cid=120797894}}</ref>{{rp|169}}  In his 1913 paper Bohr cites Nicholson as finding quantized angular momentum important for the atom.<ref name="bohr1"/>

The other critical influence of Nicholson work was his detailed analysis of spectra. Before Nicholson's work Bohr thought the spectral data was not useful for understanding atoms. In comparing his work to Nicholson's, Bohr came to understand the spectral data and their value. When he then learned from a friend about [[Balmer formula|Balmer's compact formula]] for the spectral line data, Bohr quickly realized his model would match it in detail.<ref name="McCormmach1966"/>{{rp|178}}

Nicholson's model was based on classical electrodynamics along the lines of [[J.J. Thomson]]'s [[plum pudding model]] but his negative electrons orbiting a positive nucleus rather than circulating in a sphere.  To avoid immediate collapse of this system he required that electrons come in pairs so the rotational acceleration of each electron was matched across the orbit.<ref name="McCormmach1966"/>{{rp|163}} By 1913 Bohr had already shown, from the analysis of alpha particle energy loss, that hydrogen had only a single electron not a matched pair.<ref name=PaisInwardBound/>{{rp|195}} Bohr's atomic model would abandon classical electrodynamics.

Nicholson's model of radiation was quantum but was attached to the orbits of the electrons.<ref name="Nicholson1912">{{Cite journal |last=Nicholson |first=J. W. |date=14 June 1912 |title=The Constitution of the Solar Corona. IL |journal=Monthly Notices of the Royal Astronomical Society |publisher=Oxford University Press |volume=72 |issue=8 |pages=677–693 |doi=10.1093/mnras/72.8.677 |issn=0035-8711|doi-access=free }}</ref><ref name=Heilbron2013/>{{rp|q=An oscillator could emit or absorb radiation when its natural frequency equalled that of the radiation (ν), and then only in energy increments (E = hν), or quanta}} Bohr quantization would associate it with differences in energy levels of his model of hydrogen rather than the orbital frequency.