Title: James Chadwick
Content:  Sir James Chadwick, (20 October 1891 – 24 July 1974) was a British physicist who was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932. In 1941, he wrote the final draft of the MAUD Report, which inspired the U.S. government to begin serious atomic bomb research efforts. He was the head of the British team that worked on the Manhattan Project during World War II. He was knighted in Britain in 1945 for his achievements in physics. Chadwick graduated from the Victoria University of Manchester in 1911, where he studied under Ernest Rutherford (known as the "father of nuclear physics"). At Manchester, he continued to study under Rutherford until he was awarded his 
Title: James Chadwick
Content:  in 1913. The same year, Chadwick was awarded an 1851 Research Fellowship from the Royal Commission for the Exhibition of 1851. He elected to study beta radiation under Hans Geiger in Berlin. Using Geiger's recently developed Geiger counter, Chadwick was able to demonstrate that beta radiation produced a continuous spectrum, and not discrete lines as had been thought. Still in Germany when World War I broke out in Europe, he spent the next four years in the Ruhleben internment camp. After the war, Chadwick followed Rutherford to the Cavendish Laboratory at the University of Cambridge, where Chadwick earned his Doctor of Philosophy degree under Rutherford's supervision from Gonville and Caius College, Cambridge, in June 1921. He was Rutherford's assistant director 
Title: Discovery of the neutron
Content:  the Paris results, neither Rutherford nor James Chadwick at the Cavendish Laboratory believed the gamma ray hypothesis. Assisted by Norman Feather, Chadwick quickly performed a series of experiments showing that the gamma ray hypothesis was untenable. The previous year, Chadwick, J.E.R. Constable, and E.C. Pollard had already conducted experiments on disintegrating light elements using alpha radiation from polonium. They had also developed more accurate and efficient methods for detecting, counting, and recording the ejected protons. Chadwick repeated the creation of the radiation using beryllium to absorb the alpha particles: 9Be + 4He (α) → 12C + 1n. Following the Paris experiment, he aimed the radiation at paraffin wax, a hydrocarbon high in hydrogen 
Title: James Chadwick
Content:  experiments using improvised materials such as radioactive toothpaste. With the help of Charles Drummond Ellis, he worked on the ionisation of phosphorus, and the photochemical reaction of carbon monoxide and chlorine. He was released after the Armistice with Germany came into effect in November 1918, and returned to his parents' home in Manchester, where he wrote up his findings over the previous four years for the 1851 Exhibition commissioners. Rutherford gave Chadwick a part-time teaching position at Manchester, allowing him to continue research. He looked at the nuclear charge of platinum, silver, and copper, and experimentally found that this was the 
Title: Discovery of the neutron
Content:  hence offering a target dense with protons. As in the Paris experiment, the radiation energetically scattered some of the protons. Chadwick measured the range of these protons, and also measured how the new radiation impacted the atoms of various gases. He found that the new radiation consisted of not gamma rays, but uncharged particles with about the same mass as the proton. These particles were neutrons. Chadwick won the Nobel Prize in Physics in 1935 for this discovery. The year 1932 was later referred to as the "annus mirabilis" for nuclear physics in the Cavendish Laboratory, with discoveries of the neutron, artificial nuclear disintegration by the Cockcroft–Walton particle accelerator, and the positron.
Title: John Cockcroft
Content:  which French scientists had reported, but none were found. In February 1932, James Chadwick demonstrated that what had been observed were actually neutrons. Cockcroft and Walton then switched to looking for alpha particles instead. On 14 April 1932, Walton bombarded a lithium target and noticed what he thought might be alpha particles. Cockcroft and then Rutherford were summoned, and confirmed that this was indeed the case. That evening, Cockcroft and Walton met at Rutherford's home and produced a letter for Nature in which they announced their results, the first artificial disintegration of an atomic nucleus, which can be described thus: This feat was popularly known as splitting the atom. For this accomplishment, Cockcroft 
Title: James Chadwick
Content:  research at the Cavendish Laboratory for over a decade at a time when it was one of the world's foremost centres for the study of physics, attracting students like John Cockcroft, Norman Feather, and Mark Oliphant. Chadwick followed his discovery of the neutron by measuring its mass. He anticipated that neutrons would become a major weapon in the fight against cancer. Chadwick left the Cavendish Laboratory in 1935 to become a professor of physics at the University of Liverpool, where he overhauled an antiquated laboratory and, by installing a cyclotron, made it an important centre for the study of nuclear physics. During the Second World War, Chadwick carried out research as part of the Tube Alloys project to build an 
Title: James Chadwick
Content:  the Combined Policy Committee on 4 July when Field Marshal Sir Henry Maitland Wilson gave Britain's agreement to use the atomic bomb against Japan, and at the Trinity nuclear test on 16 July, when the first atomic bomb was detonated. Inside its pit was a polonium-beryllium modulated neutron initiator, a development of the technique that Chadwick had used to discover the neutron over a decade before. William L. Laurence, the New York Times reporter attached to the Manhattan Project, wrote that "never before in history had any man lived to see his own discovery materialize itself with such telling effect on the destiny of man."
Title: Discovery of nuclear fission
Content:  particles. The feat was popularly known as "splitting the atom", but was not nuclear fission; as it was not the result of initiating an internal radioactive decay process. Just a few weeks before Cockcroft and Walton's feat, another scientist at the Cavendish Laboratory, James Chadwick, discovered the neutron, using an ingenious device made with sealing wax, through the reaction of beryllium with alpha particles: Irène Curie and Frédéric Joliot irradiated aluminium foil with alpha particles and found that this results in a short-lived radioactive isotope of phosphorus with a half-life of around three minutes: which then decays to a stable isotope of silicon 
Title: Atomic theory
Content:  on electrons in metals, but James Chadwick found that the ionization effect was too strong for it to be due to electromagnetic radiation, so long as energy and momentum were conserved in the interaction. In 1932, Chadwick exposed various elements, such as hydrogen and nitrogen, to the mysterious "beryllium radiation", and by measuring the energies of the recoiling charged particles, he deduced that the radiation was actually composed of electrically neutral particles which could not be massless like the gamma ray, but instead were required to have a mass similar to that of a proton. Chadwick now claimed these particles as Rutherford's neutrons. For his discovery of the neutron, Chadwick received the Nobel Prize in 1935.

Question: what did the scientist chadwick discovered?
Answer: Neutron.