James chadwick atomic theory3/31/2024 They observed that the bombardment led to the emission of a neutral radiation from the Polonium, which was highly penetrative. In 1930, Walther Bothe and Herbert Becker conducted experiments involving bombarding the element Beryllium with alpha particles emitted from radioactive polonium. 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. Sir James Chadwick (20 October 1891 – 24 July 1974) was an English physicist, most noted for his discovery of neutrons in 1932.
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