James Chadwick’s Contribution to the Atomic Theory This theory, however, was not readily accepted by the scientific community due to lack of proof. The particle would be a composite of an electron and a proton and would be called a “neutron”. To overcome this, in 1921, Rutherford with the help of Niels Bohr put forth a theory, hypothesizing the existence of a neutral-charged particle that had the same mass of a proton. Since the electron was a constantly accelerating particle of a negative charge, it would be attracted to the positive charge of the nucleus, thus causing the atom to become unstable and implode. This model, however, had a very obvious limitation. ◈ The atomic mass correlates with the charge of the atomic core or the atomic nucleus. ◈ The electrons do not affect the pattern and trajectory of alpha particles. Hence, this model is also called the planetary model. ◈ The atom is a hollow structure with its mass and positive charge concentrated into a tiny and dense core at the center, and the negatively charged lighter electrons orbiting the core like the planetary structure. This discovery was instrumental in realizing that the atom was not a solid spherical structure. Further experiments conducted by Rutherford in collaboration with Ernest Marsden and Hans Geiger, led them to the discovery of the atomic nucleus in 1911. These rays were identified and named as alpha (α), beta (β), and gamma (γ) rays by Rutherford, based on their charge and mass. Experimentation led scientists to discover that a radioactive substance when subjected to a magnetic field, emits three types of energy rays (radiations). With the accidental discovery of radiation and radioactive materials in 1896 by Henri Becquerel, a new path emerged in the study of materials and their compositions. In his lifetime, he worked closely with outstanding scientists like Ernest Rutherford and Johannes “Hans” Wilhelm Geiger, both of whom have made various substantial and vital contributions to the field of radiation physics. He received a Nobel Prize in the field of physics in 1935 for this significant discovery. One of his best-known students was Ernest Rutherford, who succeeded Thomson as Cavendish Professor of Physics.Sir James Chadwick (20 October 1891 – 24 July 1974) was an English physicist, most noted for his discovery of neutrons in 1932. Seven of his research assistants, as well as his own son, went on to win the Nobel Prize in Physics. Thomson's greatest contribution to science to be his role as a teacher. Thomson published an important monograph in 1913 urging the use of the mass spectrograph in chemical analysis. His atomic theory helped explain atomic bonding and the structure of molecules. Thomson was closely aligned with chemists of the time.These experiments led to the development of the mass spectrograph. Thomson also investigated the nature of positively-charged particles.The son, Sir George Paget Thomson, received the Nobel Prize in Physics in 1937. In 1890, Thomson married one of his students, Rose Elisabeth Paget. So, Joseph John attended Owens College in Manchester, and then Trinity College in Cambridge, where he became a mathematical physicist. to be an engineer, but the family did not have the funds to support the apprenticeship.
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