Editing Ernest Rutherford (section)

=== Discovery of the proton ===
Together with [[Henry Moseley|H.G. Moseley]], Rutherford developed the [[atomic number|atomic numbering system]] in 1913. Rutherford and Moseley's experiments used [[cathode rays]] to bombard various elements with streams of electrons and observed that each element responded in a consistent and distinct manner. Their research was the first to assert that each element could be defined by the properties of its inner structures – an observation that later led to the discovery of the [[atomic nucleus]].<ref name="Nobel Rutherford Biography"/> This research led Rutherford to theorize that the hydrogen atom (at the time the least massive entity known to bear a positive charge) was a sort of "positive electron" – a component of every atomic element.<ref>{{cite journal |last1=Rutherford |first1=Ernest |title=The structure of the atom |journal=Philosophical Magazine |date=1914 |volume=27 |pages=488–498 |url=http://www.ub.edu/hcub/hfq/sites/default/files/ruth1914%285%29.pdf |access-date=13 June 2023 |archive-date=13 June 2023 |archive-url=https://web.archive.org/web/20230613022543/http://www.ub.edu/hcub/hfq/sites/default/files/ruth1914(5).pdf |url-status=live }}</ref><ref>{{cite book |last1=Whittaker |first1=Edmund |title=A History of the Theories of Aether and Electricity |date=1989 |volume=2 |publisher=Courier Dover Publications |isbn=0-486-26126-3 |page=87}}</ref>

It was not until 1919 that Rutherford expanded upon his theory of the "positive electron" with a series of experiments beginning shortly before the end of his time at Manchester. He found that nitrogen, and other light elements, ejected a proton, which he called a "hydrogen atom", when hit with α (alpha) particles.<ref name="Nobel Rutherford Biography"/> In particular, he showed that particles ejected by alpha particles colliding with hydrogen have unit charge and 1/4 the momentum of alpha particles.<ref>{{cite journal |last1=Rutherford |first1=Ernest |title=LII. Collision of α particles with light atoms II. Velocity of the hydrogen atom |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science |date=8 April 2009 |volume=37 |issue=222 |pages=562–571 |doi=10.1080/14786440608635917 |url=https://www.tandfonline.com/doi/abs/10.1080/14786440608635917?journalCode=tphm17 |access-date=13 June 2023 |series=6 |archive-date=13 June 2023 |archive-url=https://web.archive.org/web/20230613022542/https://www.tandfonline.com/doi/abs/10.1080/14786440608635917?journalCode=tphm17 |url-status=live }}</ref>

Rutherford returned to the Cavendish Laboratory in 1919, succeeding J. J. Thomson as the Cavendish professor and the laboratory's director, posts that he held until his death in 1937.<ref name=cam>{{cite web |url=http://www.phy.cam.ac.uk/history/cavprof.php |title=The Cavendish Professorship of Physics |publisher=University of Cambridge |accessdate=30 November 2013 |archive-date=3 July 2013 |archive-url=https://web.archive.org/web/20130703172354/http://www.phy.cam.ac.uk/history/cavprof.php |url-status=dead }}</ref> During his tenure, Nobel prizes were awarded to [[James Chadwick]] for discovering the neutron (in 1932), [[John Cockcroft]] and [[Ernest Walton]] for an experiment that was to be known as ''splitting the atom'' using a [[particle accelerator]], and [[Edward Victor Appleton|Edward Appleton]] for demonstrating the existence of the [[ionosphere]].