Editing Bohr model (section)

===Thomson's atom model===
{{main| Plum pudding model}}
When Bohr began his work on a new atomic theory in the summer of 1912<ref name="Heilbron & Kuhn 1969"/>{{rp|237}} the atomic model proposed by [[J.&nbsp;J. Thomson]], now known as the plum pudding model, was the best available.<ref name="Heilbron1985">{{Cite book |last=John L |first=Heilbron |chapter-url=https://archive.org/details/nielsbohrcentena00fren/page/38/mode/2up |title=Niels Bohr: a centenary volume |date=1985 |publisher=Harvard University Press |isbn=978-0-674-62415-3 |editor-last=French |editor-first=A. P. |location=Cambridge, Mass |chapter=Bohr's First Theories of the Atom |editor-last2=Kennedy |editor-first2=P. J.}}</ref>{{rp|37}} Thomson proposed a model with electrons rotating in coplanar rings within an atomic-sized, positively-charged, spherical volume. Thomson showed that this model was mechanically stable by lengthy calculations and was electrodynamically stable under his original assumption of thousands of electrons per atom. Moreover, he suggested that the particularly stable configurations of electrons in rings was connected to chemical properties of the atoms. He developed a formula for the scattering of [[beta decay|beta particles]] that seemed to match experimental results.<ref name=Heilbron1985/>{{rp|38}}
However Thomson himself later showed that the atom had a factor of a thousand fewer electrons, challenging the stability argument and forcing the poorly understood positive sphere to have most of the atom's mass. Thomson was also unable to explain the many lines in atomic spectra.<ref name=KraghQuantumAtom2012/>{{rp|18}}