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Drawbacks of Rutherford atomic model


The plum pudding model of the atom was one of the most widely accepted models across the globe. J. J. Thomson proposed the plum pudding model for understanding the structure of atoms. However, several experiments performed by scientists to study the atomic structure showed astonishingly different results. They contradicted the plum pudding model proposed by J.J. Thomson. This is when scientists across the globe tried to reconsider the structure of atoms and study it again.

Rutherford's gold foil experiment

In 1911, a British scientist named Ernest Rutherford carried out the famous gold foil experiment. The gold foil experiment performed by Rutherford was a breakthrough in chemistry, which helped us understand the atomic structure more accurately. In his experiment, Rutherford locked a source of alpha particles in a lead container containing a tiny slit. He, thus, ensured that the alpha particles traveled in a single straight line.

Next, Rutherford bombarded these alpha particles onto a thin gold sheet which was in turn surrounded by a fluorescent screen. Finally, the fluorescent screen was placed to detect the radiation. So, whenever an alpha particle hit the fluorescent screen, the screen emitted fluorescent light.

In Rutherford's experiment, the alpha particles emitted from the radioactive source were made to hit the gold foil. As we know, Thomson's plum pudding model suggested that an atom is a sphere of positive charge containing negative charges embedded in it. If we assume that Thomson's model was suitable, alpha particles were expected to pass right through the atoms and hit the screen straight.

However, what Rutherford observed was astonishing. He observed that most of the fast-moving alpha particles passed straight through the foil and hit the screen straight. These particles which hit the detector (screen) straight were called non-deflected particles. A few particles get deflected by small angles, whereas some of them also rebound. Let us now understand the inferences he made based on his observations.

Observations and Inferences

The observations made by Ernest Rutherford helped him come to the following conclusions.

● The alpha particles that were bombarded onto the gold sheet passed through the same without undergoing any deflection. This indicates that the majority of the space in the atom is vacant or empty.
● One of his observations stated that minimal angles deflected a few alpha particles. This observation led him to conclude that positive charge was not uniformly distributed in an atom, as said by Thomson.
● According to his third observation, a small number of particles also got rebound. This observation led him to conclude that the positive charge exclusively occupied a small volume of the atom.

Rutherford atomic model

Based on his observations and inferences, Rutherford came up with a more valid theory for the atomic structure. His theory for explaining the structure of atoms is called the Rutherford atomic model. The Rutherford atomic model is summarized as follows.

● The majority of the space inside the atom is unoccupied or empty.
● The volts are because the positive charge of the atom occupies them is extremely small. This region where the positive charge of the atom is concentrated is called the nucleus.
● The Rutherford atomic model proposed that electrons (negatively charged particles) revolve around the atom in circular paths. The circular concrete paths in which the electrons revolve are called orbits.
● Electrons (negatively charged particles) and nuclei (positively charged particles) were said to be held together with the help of strong electrostatic forces.

This was all about the gold foil experiment and the Rutherford atomic model. Although the Rutherford atomic model came up with the facts regarding the atomic structure, it does offer a few drawbacks. In the next section of this article, let us understand the drawbacks of the Rutherford atomic model.

Drawbacks of the Rutherford atomic model

Many scientists questioned and challenged Rutherford's atomic model. Rutherford, in his model of atomic structure, did not address a few significant issues. The issues or drawbacks which Rutherford did not address in his atomic model are as follows.

● Rutherford did not explain the revolution of electrons in circular concrete paths called orbits. Instead, Rutherford proposed that electrons constantly revolved around the nucleus but could not explain their stability. Here is the reason why the stability of the electrons in circular paths is questioned. Any particle in a circular motion undergoes acceleration and changes direction constantly.

Hence, the particle in a circular motion should radiate energy as a result of acceleration. However, the electrons would ultimately lose energy and fall towards the nucleus making the atom highly unstable.

On the contrary, we know that atoms are very stable. Rutherford was able to effectively determine that every atom consisted of a positively charged nucleus. However, he could not explain how the electrons revolve around the nucleus.

● In addition to the stability of electrons in orbits, Rutherford did not mention anything regarding the arrangement of electrons in the atom. Hence, his theory of atomic structure remained incomplete.

The Rutherford atomic model could not explain the arrangement and stability of electrons in the orbits, making it incomplete. However, the Rutherford atomic model stood as a base for further advancements in quantum mechanics.

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