Editing Rutherford scattering experiments (section)

==Notes on historical measurements==
Rutherford assumed that the radius of atoms in general to be on the order of 10<sup>−10</sup> m and the positive charge of a gold atom to be about 100 times that of hydrogen ({{val|100|u=''q''<sub>e</sub>}}).<ref name="Rutherford1911"/> The atomic weight of gold was known to be around 197 since early in the 19th century.<ref>{{Cite journal |last=van Spronsen |first=Jan W. |date=1967-01-01 |title=The History and Prehistory of the Law of Dulong and Petit as Applied to the Determination of Atomic Weights |url=https://online.ucpress.edu/hsns/article/doi/10.2307/27757279/33559/The-History-and-Prehistory-of-the-Law-of-Dulong |journal=Chymia |language=en |volume=12 |pages=157–169 |doi=10.2307/27757279 |jstor=27757279 |issn=0095-9367|url-access=subscription }}</ref> From an experiment in 1906, Rutherford measured alpha particles to have a charge of {{val|2|u=''q''<sub>e</sub>}} and an atomic weight of 4, and alpha particles emitted by [[radon]] to have velocity of {{val|1.70|e=7|u=m/s}}.<ref>[[#refRutherford1906|Rutherford (1906)]].</ref> Rutherford deduced that alpha particles are essentially helium atoms stripped of two electrons, but at the time scientists only had a rough idea of how many electrons atoms have and so the alpha particle was thought to have up to 10 electrons left.<ref name=Heilbron1968/>{{rp|285}} In 1906, J. J. Thomson measured the [[elementary charge]] to be about {{val|3.4|e=-10|u=esu}} ({{val|1.3|e=-19|u=C}}).<ref>Edmund Edward Fournier d'Albe (1906). ''The Electron Theory'', p. 37</ref> In 1909 [[Robert A. Millikan]] provided a more accurate measurement of {{val|1.5924|e=-19|u=[[coulomb|C]]}}, only 0.6% off the current accepted measurement. [[Jean Perrin]] in 1909 measured the mass of the hydrogen atom to be {{val|1.43|e=-27|u=kg}},<ref>[[#refPerrin1909|Perrin (1909), p. 49]]</ref> and if an alpha particle is four times as heavy as that, it would have an absolute mass of {{val|5.72|e=-27|u=kg}}.

The convention in Rutherford's time was to measure charge in [[electrostatic unit]]s, distance in centimeters, force in [[dyne]]s, and energy in [[erg]]s. The modern convention is to measure charge in [[coulomb]]s, distance in meters, force in [[Newton (unit)|newton]]s, and energy in [[joule]]s. Using coulombs requires using the [[Coulomb constant]] in certain equations. In this article, Rutherford and Thomson's equations have been rewritten to fit modern notation conventions.