Nowadays, it is widely known that atoms are neutral particles containing protons, electrons, and neutrons, positive, negative, and neutral charge-wise. However, this was not the case several centuries back. There were several hypotheses and conspiracies regarding the topic of Rutherford’s Atomic Model, and the only known fact was that the atom is a very small indivisible particle that forms all the objects of the universe.
This was changed only when the first atomic model was proposed. In the initial ages, the plum pudding model by J.J. Thompson was the widely accepted model of the atom. This model proposed that the atom in its entirety is a positively charged sphere that consists of several negatively charged particles which are embedded within the sphere.
The British scientist Ernst Rutherford noticed several incompetencies and unexplained discrepancies with the model comparing the atom with a plum pudding. Therefore, he came up with a new model of the atom and his hypothesis, which provided more extensive insight into several concerns that the previous model did not answer.
Every student is required to know the Rutherford Atomic Model Experiment and Limitations. Here is a simple explanation to facilitate better understanding.
Rutherford’s Alpha Scattering Experiment
This experiment, in a nutshell, included a thin gold foil that was bombarded with a stream of alpha particles from a high energy radioactive source. The trajectory with which these alpha particles bounced off from the gold sheet was then studied. This deflection was analysed with the help of a fluorescent zinc sulphide screen placed around the gold foil sheet.
Observations of Rutherford’s Alpha Scattering Experiment
Upon performing these experiments, Rutherford drew the following observations, which heavily contradicted the principles of the Thomson model.
- Several particles passed right through the gold foil without any deviation. This indicated that there was a significant amount of empty space in the atom, which was devoid of any charge and energy.
- A few waves were deflected but at very short angles. This was an indicator proving that the positively charged particles were not distributed evenly across the atom. Rather, they were concentrated more towards a single area.
- Only a very few particles were deflected completely with the perfect 180-degree angle. This showed that positively charged particles occupied a volume that was several times lesser than the volume and space occupied by the entire atom itself.
Rutherford’s Atomic Model
Based on the observations made from the above experiment, Rutherford came up with the following postulates, thereby framing a new model of the atom, which held significant differences from the previously accepted atomic model. The following were the postulates proposed by Rutherford to support his model.
- All the positively charged particles in the atom are concentrated within a very small volume which holds most of the mass of the atom. This area is called the nucleus of the atom.
- The negatively charged particles revolve around this positively charged cluster following specific paths, which are known as orbits. He also claimed that the electrons move at exceptionally high speeds along these circular orbits.
- Since the nucleus is highly loaded with a positive charge and the electrons on the outside bear a high amount of negative charge, they are held together in a stable manner with the help of electrostatic forces.
This was a breakthrough in atomic sciences as this helped explain the confusions and concerns of several other scientists and atomic enthusiasts of the time. This was a milestone in atomic science as the discovery of the nucleus led to several other advances that were not possible otherwise.
Limitations of Rutherford’s Atomic Model
Though Rutherford’s atom model answered several questions left unanswered by the plum-pudding model and all other previous propositions regarding the structure of the atom, there were still a few concerns and specifics that the British scientist did not address.
The following were the essential aspects that Rutherford’s model of the atom could not clarify.
- Stability of the atom: Rutherford suggested that the negatively charged particles revolve around the positively charged nucleus in a fixed circular path called the orbit. This clashed with the Maxwell theory, which states that any accelerated particle with a charge is sure to emit electromagnetic radiation.
- This implies that the electrons revolving around the nucleus with a significantly high amount of acceleration should produce a decent amount of electromagnetic radiation.
- Emission of electromagnetic energy from the electrons would result in the loss of the electron’s energy, directly affecting their motion. This would cause further reduction in the orbit’s size and finally result in the collapse of the atom itself.
- According to calculations with the above statements in mind, studies have shown that the atom would collapse within a very short period of time, ranging from 8 to 10 seconds. This was the most significant drawback of the model proposed by Rutherford.
- The second drawback of the model was that there was no explanation regarding the electrons’ positioning and arrangement in the atom’s fixed orbits.
- There was no adequate information about the atomic emission spectra of hydrogen.
Despite all the above incompetencies of the atomic model proposed by Ernst Rutherford, he is still one of the most significant figures in the field of atomics because of his significant contribution. There are many discrepancies in the model but the discovery of the nucleus and the presence of electrons trumped over it all.
This atomic model was also the base for several other scientists like Niels Bohr, James Chadwick and several others who made additional improvements to the theory of atoms and performed more elaborate experiments in the future.
In conclusion, Rutherford’s model of the atom will always be marked as an important timestamp in the scientific field because it was the basic foundation for several important branches of science, mainly quantum mechanics. It also changed the overall outlook of physicists, thereby allowing several new developments that led to the formulation of currently studied modern physics.
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