Editing Rutherford scattering experiments (section)

===Alpha particles and the Thomson atom===
An [[alpha particle]] is a positively charged particle of matter that is spontaneously emitted from certain radioactive elements. Alpha particles are so tiny as to be invisible, but they can be detected with the use of phosphorescent screens, photographic plates, or electrodes. Rutherford discovered them in 1899.<ref>{{cite journal |author=Ernest Rutherford |year=1899 |title=Uranium Radiation and the Electrical conduction Produced by it |journal=Philosophical Magazine |volume=47 |issue=284 |pages=109–163|url=https://archive.org/details/londonedinburgh5471899lon/page/108/mode/2up}}</ref> In 1906, by studying how alpha particle beams are deflected by magnetic and electric fields, he deduced that they were essentially [[helium]] atoms stripped of two electrons.<ref>{{cite journal
 |author1=Ernest Rutherford
 |year=1906
 |title=The Mass and Velocity of the α particles expelled from Radium and Actinium
 |journal=Philosophical Magazine |series=Series 6
 |volume=12
 |issue=70
 |pages=348–371
 |doi=10.1080/14786440609463549 
 |url=https://zenodo.org/record/1430814
 |ref=refRutherford1906
 }}</ref> Thomson and Rutherford knew nothing about the internal structure of alpha particles. At the time, scientists did not know exactly how many electrons a helium atom had (nor atoms of other elements for that matter), so a helium atom stripped of two electrons might still have ten or so left for all they could tell.<ref name=Heilbron1968/>{{rp|280|q=The α particle, because of its mass, was considered a formidable projectile of ''atomic dimensions''}}

Thomson's model was consistent with the experimental evidence available at the time. Thomson studied [[beta particle]] scattering which showed small angle deflections modelled as interactions of the particle with many atoms in succession. Each interaction of the particle with the electrons of the atom and the positive background sphere would lead to a tiny deflection, but many such collisions could add up.<ref name=Heilbron1968/>{{rp|274}} The scattering of alpha particles was expected to be similar.<ref name=Heilbron1968/>{{rp|281|q=...Rutherford and his colleagues followed the multiple scattering approach in the case of α particles as well}} Rutherford's team would show that the multiple scattering model was not needed: single scattering from a compact charge at the centre of the atom would account for all of the scattering data.<ref name=Heilbron1968/>{{rp|289}}