Ernest Rutherford: Difference between revisions - Wikipedia

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In 1921, while working with [[Niels Bohr]] (who postulated that electrons moved in specific orbits), Rutherford theorized about the existence of [[neutron]]s, (which he had christened in his 1920 [[Bakerian Lecture]]), which could somehow compensate for the repelling effect of the positive charges of [[proton]]s by causing an attractive [[nuclear force]] and thus keep the nuclei from flying apart from the repulsion between protons. The only alternative to neutrons was the existence of "nuclear electrons" which would counteract some of the proton charges in the nucleus, since by then it was known that nuclei had about twice the mass that could be accounted for if they were simply assembled from hydrogen nuclei (protons). But how these nuclear electrons could be trapped in the nucleus, was a mystery.

Rutherford is widely quoted as saying, regarding the results of these experiments: "It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you."<ref>{{Cite book|chapter=Ernest Rutherford|year=2016 |chapter-url=https://www.oxfordreference.com/display/10.1093/acref/9780191826719.001.0001/q-oro-ed4-00009051 |language=en|doi=10.1093/acref/9780191826719.001.0001 |isbn=978-0-19-182671-9 |editor-last1=Ratcliffe |editor-first1=Susan }}</ref>

Rutherford's theory of [[neutron]]s was proved in 1932 by his associate [[James Chadwick]], who recognized neutrons immediately when they were produced by other scientists and later himself, in bombarding beryllium with alpha particles. In 1935, Chadwick was awarded the Nobel Prize in Physics for this discovery.