James Chadwick was an English physicist, well known for his discovering neutrons in the year 1932. He acquired a Nobel Prize in the physics discipline in the year 1935 for this substantial discovery. Throughout his lifetime, he closely worked with exceptional scientists like Johannes “Hans” Wilhelm Geiger and Ernest Rutherford, both of whom have worked on a variety of essential and considerable contributions to the radiation physics field.
With Henri Becquerel’s accidental discovery of radioactive materials in the year 1896, a new path arose in the materials and their composition’s study. Through experimentation, scientists found out that, when a radioactive substance is exposed to a magnetic field, it emits 3 types of radiations. As mentioned during our Physics tuition classes, these radiations were recognized and named as gamma, alpha, and beta rays by Rutherford, on the basis of their mass and charge. Additional experiments carried out by Rutherford in cooperation with Hans Geiger and Ernest Marsden, led to the atomic nucleus discovery in the year 1911. The discovery was contributory in knowing that the atom wasn’t a solid spherical structure.
The Rutherford’s Atomic Model
The Rutherford’s atomic model postulated:
– The structure of an atom is hollow, with its positive charge and mass concerted into a dense and small core at its center, and negatively charged electrons, which are lighter, orbiting the core resembling structure of the planetary. Thus, Rutherford’s model is also referred to as the planetary model.
– The atomic mass relates with the atomic nucleus or the atomic core charge.
– The electrons don’t influence the trajectory and pattern of alpha particles.
However, Rutherford’s model had an evident limitation. Thai is, considering that the electron was consistently accelerating and has a negative charge, eventually, it would be pulled to the nucleus, which is positively charged, as a result making the atom unstable and finally implode. To conquer this limitation, with the assistance of Niels Bohr, Rutherford came up with a theory which hypothesized the existence of a “neutron” which was a neutral-charged particle, and had the exact same mass as a proton. However, this concept wasn’t readily accepted into the scientific field because of lack of proof.
The Modified Atomic Theory
The discovery of neutrons reformed the atomic structure understanding. It ascertained the validity of the Rutherford’s atomic model and expounded on its stability. The following postulates were included into the atomic theory:
– An atom’s nucleus is made up of subatomic particles named nucleons.
– There are two types of nucleons: neutrons and protons.
– Neutrons have the same mass as a proton and are neutrally charged.
– A neutron comprises of a proton and electron couple.
– The total mass of the neutrons and protons gives an element’s atomic mass.
Later, through a series of experiments, Werner Heisenberg, a German physicist, proved that a neutron is a particle on its own and not a composition of a proton and an electron.