Editing Proton (section)

== History ==
The concept of a hydrogen-like particle as a constituent of other atoms was developed over a long period. As early as 1815, [[William Prout]] proposed that all atoms are composed of hydrogen atoms (which he called "protyles"), based on a simplistic interpretation of early values of [[atomic weight]]s (see [[Prout's hypothesis]]), which was disproved when more accurate values were measured.<ref name="Lecturer2006" />{{rp|39–42}}
[[File:Rutherford 1911 Solvay.jpg|thumb|150px|[[Ernest Rutherford]] at the first [[Solvay Conference]], 1911]]
[[File:Proton detected in an isopropanol cloud chamber.jpg|thumb|Proton detected in an [[isopropanol]] [[cloud chamber]]]]
In 1886, [[Eugen Goldstein]] discovered [[canal rays]] (also known as anode rays) and showed that they were positively charged particles (ions) produced from gases. However, since particles from different gases had different values of [[charge-to-mass ratio]] (''q''/''m''), they could not be identified with a single particle, unlike the negative [[electron]]s discovered by [[J. J. Thomson]]. [[Wilhelm Wien]] in 1898 identified the hydrogen ion as the particle with the highest charge-to-mass ratio in ionized gases.<ref name="Wien1904" />

Following the discovery of the atomic nucleus by [[Ernest Rutherford]] in 1911, [[Antonius van den Broek]] proposed that the place of each element in the [[periodic table]] (its atomic number) is equal to its nuclear charge. This was confirmed experimentally by [[Henry Moseley]] in 1913 using [[X-ray spectroscopy|X-ray spectra]] (More details in [[Atomic number]] under Moseley's 1913 experiment).

In 1917, Rutherford performed experiments (reported in 1919 and 1925) which proved that the hydrogen nucleus is present in other nuclei, a result usually described as the discovery of protons.<ref name="Petrucci2002" /> These experiments began after Rutherford observed that when [[alpha particles]] would strike air, Rutherford could detect scintillation on a [[zinc sulfide]] screen produced at a distance well beyond the distance of alpha-particle range of travel but instead corresponding to the range of travel of hydrogen atoms (protons).<ref>{{cite web |title=How Rutherford detects proton and life of Rutherford |url=https://www.sciencedirect.com/topics/mathematics/rutherford |website=ScienceDirect |access-date=6 December 2023 |archive-date=5 December 2023 |archive-url=https://web.archive.org/web/20231205185436/https://www.sciencedirect.com/topics/mathematics/rutherford |url-status=live }}</ref> After experimentation, Rutherford traced the reaction to the nitrogen in air and found that when alpha particles were introduced into pure nitrogen gas, the effect was larger. In 1919, Rutherford assumed that the alpha particle merely knocked a proton out of nitrogen, turning it into carbon. After observing Blackett's cloud chamber images in 1925, Rutherford realized that the alpha particle was absorbed. If the alpha particle were not absorbed, then it would knock a proton off of nitrogen creating 3 charged particles (a negatively charged carbon, a proton, and an alpha particle). It can be shown<ref>{{cite journal |title=Blackett's cloud chamber |journal=Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character |date=2 February 1925 |volume=107 |issue=742 |pages=349–360 |doi=10.1098/rspa.1925.0029 |doi-access=free }}</ref> that the 3 charged particles would create three tracks in the cloud chamber, but instead only 2 tracks in the cloud chamber were observed. The alpha particle is absorbed by the nitrogen atom. After capture of the alpha particle, a hydrogen nucleus is ejected, creating a net result of 2 charged particles (a proton and a positively charged oxygen) which make 2 tracks in the cloud chamber. Heavy oxygen (<sup>17</sup>O), not carbon or fluorine, is the product. This was the first reported [[nuclear reaction]], {{chem2|^{14}N + α → ^{17}O + p}}. Rutherford at first thought of our modern "p" in this equation as a hydrogen ion, {{chem2|H+}}.

Depending on one's perspective, either 1919 (when it was seen experimentally as derived from another source than hydrogen) or 1920 (when it was recognized and proposed as an elementary particle) may be regarded as the moment when the proton was 'discovered'.

Rutherford knew hydrogen to be the simplest and lightest element and was influenced by [[Prout's hypothesis]] that hydrogen was the building block of all elements. Discovery that the hydrogen nucleus is present in other nuclei as an elementary particle led Rutherford to give the hydrogen nucleus {{chem2|H+}} a special name as a particle, since he suspected that hydrogen, the lightest element, contained only one of these particles. He named this new fundamental building block of the nucleus the ''proton'', after the neuter singular of the Greek word for "first", {{lang|grc|πρῶτον}}. However, Rutherford also had in mind the word ''protyle'' as used by Prout. Rutherford spoke at the [[British Association for the Advancement of Science]] at its [[Cardiff]] meeting beginning 24 August 1920.<ref name="NatureScience" /> At the meeting, he was asked by [[Oliver Lodge]] for a new name for the positive hydrogen nucleus to avoid confusion with the neutral hydrogen atom. He initially suggested both ''proton'' and ''prouton'' (after Prout).<ref name="Romer1997" /> Rutherford later reported that the meeting had accepted his suggestion that the hydrogen nucleus be named the "proton", following Prout's word "protyle".<ref name="Footnote" /> The first use of the word "proton" in the scientific literature appeared in 1920.<ref>OED{{OED|term=proton|access-date=24 March 2021}}</ref><ref name="Pais1986" />