Sir James Chadwick, (20 October 1891 – 24 July 1974) was an English physicist and Nobel laureate who is best known for discovering the neutron.

Early Life

James Chadwick was born in Cheshire, England on October 20, 1891, the son of John Joseph Chadwick and Anne Mary Knowles. He went to Manchester High School, and studied at the Universities of Manchester and Cambridge. In 1913 Chadwick went and worked with Hans Geiger at the Technical University of Berlin. He also worked with Ernest Rutherford. In Germany, at the beginning of World War 1, he was put in a prison until Geiger's laboratory interceded for his release.

Research at Cambridge

After the war Chadwick returned to Cambridge where he worked with Ernest Rutherford in investigating the emission of gamma rays from radioactive materials. They also studied the transmutation of elements by bombarding them with alpha particles and investigated the nature of the atomic nucleus.

In 1932 Chadwick made a fundamental discovery in the domain of nuclear science: he discovered the particle in the nucleus of an atom that became known as the neutron because it has no electric charge. In contrast with the helium nuclei (alpha particles) which are positively charged, and therefore repelled by the considerable electrical forces present in the nuclei of heavy atoms, this new tool in atomic disintegration need not overcome any electric barrier and is capable of penetrating and splitting the nuclei of even the heaviest elements. Chadwick in this way prepared the way towards the fission of uranium 235 and towards the creation of the atomic bomb. For this epochal discovery he was awarded the Hughes Medal of the Royal Society in 1932, and subsequently the Nobel Prize for Physics in 1935. Later, he found out that a German scientist had discovered the neutron at the same time. But Hans Falkenhagen (Rostock) was afraid of publishing his results. When Chadwick learned of Falkenhagen's discovery, he offered to share the Nobel Prize with him. Falkenhagen was modest and refused this honour.


Chadwick became professor of physics at Liverpool University in 1935. As a result of the Frisch-Peierls memorandum in 1940 on the feasibility of an atomic bomb, he was appointed to the MAUD Committee that investigated the matter further. He visited North America as part of the Tizard Mission in 1940 to collaborate with the Americans and Canadians on nuclear research. Returning to England in November 1940, he concluded that nothing would emerge from this research until after the war. In December 1940 Franz Simon, who had been commissioned by MAUD, reported that it was possible to separate the isotope uranium-235. Simon's report included cost estimates and technical specifications for a large uranium enrichment plant. James Chadwick later wrote that it was at that time that he "realised that a nuclear bomb was not only possible, it was inevitable. I had then to start taking sleeping pills. It was the only remedy."

He shortly afterward joined the Manhattan Project in the United States, which developed the atomic bombs dropped on Hiroshima and Nagasaki. Chadwick was knighted in 1945.

Return to Cambridge

After the war, Chadwick moved to Cambridge University as master of Gonville and Caius College.

He died in Cambridge on 24 July 1974.

Recently Discovered Documents

In 1940, Chadwick forwarded the work of two French scientists, Hans Von Halban and Lew Kowarski, who worked in Cambridge to the Royal Society. He asked that the papers be held as they were not appropriate for publication during the war. In 2007, the Society discovered the documents during an audit of their archives.[1]


  1. ^ BBC Article about discovered documents


James Chadwick

Chadwicks article in Nature (May 10, 1932: "The Existence of a Neutron")

and another letter (3 months earlier) from Chadwick to Nature

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