James Chadwick and the Neutron

james chadwick

Core Concepts

In this article you will learn about the history of James Chadwick and his Nobel Prize. In addition, you will understand his contributions to nuclear physics following his discovery of the neutron.

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Who is James Chadwick?

James Chadwick was an English physicist who won the Nobel Prize in Physics in 1935 for discovering the neutron. James Chadwick was born in Manchester, England, on October 20, 1891. Chadwick passed away on July 24, 1974, in Cambridge, Cambridgeshire.

Biography of James Chadwick

Chadwick received his education at the University of Manchester, where he collaborated with Ernest Rutherford and graduated with a master’s in 1913. Later, at Berlin’s Technische Hochschule, he studied under Hans Geiger. When World War I started, they held him captive in a camp at Ruhleben for civilians. Despite spending the whole war there, he managed to do important scientific work.

Chadwick returned to England after the war to study under Rutherford at the University of Cambridge. After earning his PhD in 1921, Cambridge’s Cavendish Laboratory named him assistant director of research in 1923. When James and Rutherford were investigating the nature of the atomic nucleus, they discovered that the proton, the nucleus of the hydrogen atom, is a component of the nuclei of other atoms. They did this by blasting the elements with alpha particles to study the transmutation of elements.

In 1935, the University of Liverpool granted Chadwick a physics professorship. Additionally, in 1940, he became a member of the MAUD Committee, a group established to assess the viability of the atomic bomb. By 1941, the committee reached the conclusion that the Otto Frisch and Rudolf Peierls report from 1940 was accurate. They determined that a critical mass of only around 10 kilos of uranium-235 was required.

Later, according to Chadwick, he understood “that a nuclear weapon was not only feasible, but inevitable. I had to take sleeping medications at that point. It was the only solution. The findings of the MAUD Committee had an important role in advancing the American atomic bomb development. In 1943, they appointed him as the leader of the British mission to the Manhattan Project in Los Alamos, New Mexico, in the United States. He quickly made friendly with Gen. Leslie Groves, who oversaw the project.

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James Chadwick and his Nobel Prize

Chadwick’s demonstration of neutron existence in 1932 paved the door for the fission of uranium 235 and the development of the atomic bomb. In 1932, the Royal Society awarded him the Hughes Medal, and three years later, in 1935, he earned the Physics Nobel Prize. In that same year, he was selected to occupy the Lyon Jones Chair of Physics at the University of Liverpool.

Experimentation Leading to Nobel Prize

In an experiment, he struck Beryllium with alpha particles produced by the radioactive decay of polonium naturally. High radiation penetration through a lead shield was seen, which the then-current particle theories were unable to account for. Chadwick’s interpretation issues, however, were easily resolved with the postulate of an uncharged particle that was roughly the same weight as a proton. As a result, his findings could be interpreted in terms of the known laws of nature, particularly with regard to the conservation of energy and momentum.

Later tests have verified the finding, which is especially astounding in light of the discovery of nuclear fission.

What is the Neutron Chadwick Discovered?

The neutron is a subatomic particle with the symbol n that is slightly heavier than a proton and has a neutral charge. Atomic nuclei consist of protons and neutrons. We refer to protons and neutrons as ‘nucleons’ due to their similar functions inside the nucleus and their approximate mass of one dalton. Nuclear physics explains their interactions and characteristics. Because each proton and neutron consists of three quarks, they cannot be considered fundamental particles.

With a typical lifespan of under 15 minutes, a free neutron decays to a proton, electron, and antineutrino. Because the mass of the neutron is a little bit more than that of the proton, this radioactive decay, known as beta decay, is feasible. Proton in free form is stable. However, depending on the nuclide, neutrons or protons contained in a nucleus can be either stable or unstable. The weak force controls beta decay, which occurs when neutrons transform into protons or vice versa. Neutrinos and electrons, or their antiparticles, must be emitted or absorbed for beta decay to occur.

Further Reading

If you are interested on learning more about the neutron, this is for you!