Sir James Chadwick (October 20, 1891 - July 24, 1974) was an English physicist and Nobel laureate.

Chadwick was born in Cheshire, England and educated at Manchester University and Cambridge University.

In 1914 Chadwick went to study under Hans Geiger at the Technische Hochschule in Berlin (today the Technical University of Berlin). During the First World War Chadwick was interned in Germany as an enemy alien.

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 and during the Second World War he joined the Manhattan Project in the United States, developing the atomic bombs dropped on Hiroshima and Nagasaki. Chadwick was knighted in 1945.

After the war Chadwick returned to Liverpool University until moving to Cambridge University (1948 - 1958).

He died in Cambridge.

External links

• James Chadwick (http://www.nobel-winners.com/Physics/sir_james_chadwick.html)
• Chadwicks article in Nature (May 10, 1932: "The Existence of a Neutron") (http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Chadwick-1932/Chadwick-neutron.html)
• and another letter (3 months earlier) from Chadwick to Nature (http://www.physik.uni-muenchen.de/leifiphysik/web_ph12/originalarbeiten/chadwick/chadwick_neutr.htm)