James Chadwick

PHYSICIST NAME: James Chadwick
STUDENT NAME: Angela Mari Peralta

BIOGRAPHY

BIOGRAPHY
• James Chadwick was born in Cheshire, England, on 20th October, 1891
• son of John Joseph Chadwick and Anne Mary Knowles.
• attended Manchester High School prior to entering Manchester University in 1908;
• graduated from the Honours School of Physics in 1911
• spent the next two years under Professor (later Lord) Rutherford in the Physical Laboratory in Manchester, where he worked on various radioactivity problems, gaining his M.Sc. degree in 1913.
• That same year he was awarded the 1851 Exhibition Scholarship and proceeded to Berlin to work in the Physikalisch Technische Reichsanstalt at Charlottenburg under Professor H. Geiger.
• During World War I, he was interned in the Zivilgefangenenlager, Ruhleben. After the war, in 1919, he returned to England to accept the Wollaston Studentship at Gonville and Caius College, Cambridge, and to resume work under Rutherford, who in the meantime had moved to the Cavendish Laboratory, Cambridge.
• He was elected Fellow of Gonville and Caius College (1921-1935) and became Assistant Director of Research in the Cavendish Laboratory (1923).
• In 1927 he was elected a Fellow of the Royal Society.
• In 1932, Chadwick made a fundamental discovery in the domain of nuclear science
• he was awarded the Hughes Medal of the Royal Society in 1932, and subsequently the Nobel Prize for Physics in 1935.
• He remained at Cambridge until 1935 when he was elected to the Lyon Jones Chair of Physics in the University of Liverpool. From 1943 to 1946 he worked in the United States as Head of the British Mission attached to the Manhattan Project for the development of the atomic bomb.
• He returned to England and, in 1948, retired from active physics and his position at Liverpool on his election as Master of Gonville and Caius College, Cambridge. He retired from this Mastership in 1959. From 1957 to 1962 he was a part time member of the United Kingdom Atomic Energy Authority.
• Chadwick has had many papers published on the topic of radioactivity and connected problems and, with Lord Rutherford and C. D. Ellis, he is co-author of the book Radiations from Radioactive substances (1930).
• Sir James was knighted in 1945. Apart from the Hughes Medal (Royal Society) mentioned above, he received the Copley Medal (1950) and the Franklin Medal of the Franklin Institute, Philadelphia (1951). He is an Honorary Fellow of the Institute of Physics and, in addition to receiving honorary doctorate degrees from the Universities of Reading, Dublin, Leeds, Oxford, Birmingham, Montreal (McGill), Liverpool, and Edinburgh, he is a member of several foreign academies, being Associé oft he Académie Royale de Belgique; Foreign Member of the Kongelige Danske Videnskabernes Selskab and the Koninklijke Nederlandse Akademie van Wetenschappen; Corresponding Member of the Sächsische Akademie der Wissenschaften, Leipzig; Member of the Pontificia Academia Scientiarum and the Franklin Institute; Honorary Member of the American Philosophical Society and the American Physical Society.
• In 1925, he married Aileen Stewart-Brown of Liverpool. They have twin daughters, and live at Denbigh, North Wales. His hobbies include gardening and fishing.
• Sir James Chadwick died on July 24, 1974.

CONTRIBUTIONS

• Chadwick prepared the way towards the fission of uranium 235 and towards the creation of the atomic bomb. For this epoch-making discovery
• During his period of study in Germany, Chadwick discovered that β -rays (electrons) are emitted in a continuous spectrum, at odds with other groups' results, and a finding that eventually led to the theory and discovery of the neutrino.
• Chadwick's first research upon his return to England involved the disintegration of different nuclei.
• It was in the investigation of beryllium disintegration in 1932 that the neutron was discovered. Since the neutron has no charge, the typical electromagnetic methods of detection were useless. Chadwick bounced the mystery particle off atomic nuclei that were detectable, and, by the conservation of momentum and energy, he was able to determine that the neutron had a mass slightly greater than that of a proton.
• With the discovery of the neutron as a fundamental particle, many paradoxes of physics and chemistry were finally resolved, and new areas of research evolved. Prior to the discovery of the neutron as a fundamental particle, scientists generally believed that the nucleus was comprised of protons and "nuclear electrons." However, one could not explain, for example, the spin of nuclei with that model. Now, at last, theory could predict the properties of the nucleus quite well. Also, since neutrons are not repelled by the charge on the atomic nucleus, they interact easily with nuclei. Neutron scattering enables the determination of crystal structures by probing the positions of nuclei in a sample. Neutrons can also catalyze fission reactions, for example, the fission of uranium nuclei that led to the creation of nuclear power plants and the atomic bomb.
• Chadwick played a prominent role in the effort to create the atomic bomb, both in England, and, beginning in 1943, as the leader of the British effort on the Manhattan Project.

OBJECT OF INTEREST

• Nuclear physics: He identified the neutron as part of the nucleus of atom. : He proved the existence of neutrons - elementary particles devoid of any electrical charge. In contrast with the helium nuclei (alpha rays) which are 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.
• Atomic physics: He had his early research on radioactivity. Chadwick recognized that the properties of radiation was more consistent than Rutherford's described neutral particle. Subsequent experiments from the derived information allowed Chadwick to prove the existence of the neutron


References:
Brown, Andrew (1997). The Neutron and the Bomb. New York: Oxford University Press.
http://www.jstor.org/pss/3087224
http://www.vzhang.com/vzfiles/james_chadwick.htm
http://www.helium.com/items/225599-how-james-chadwick-discovered-the-neutron
http://www.chemistryexplained.com/Ce-Co/Chadwick-James.html