Rutherford model of atom

We know that an atom’s structure is made up of electrons, protons, neutrons. After multiple scientists devised various models, this was accurately conveyed. Ernest Rutherford proposed the Rutherford atomic model, often known as the Rutherford Atom Model. However, it is no longer thought to be an accurate picture of an atom. 

Rutherford Gold Foil Model Experiment

In Rutherford’s experiment, high-energy streams of alpha-particles were battered on a thin gold foil with a thickness of 100 nm. The alpha-particle streams were ejected from a radioactive source. He carried out the experiment to investigate the deviation in the track of alpha-particles after they collided with a thin sheet of gold. He surrounded the gold foil with a screen constructed of zinc sulphide to analyse the deflection. Rutherford’s observations were in direct opposition to J J Thomson’s plum pudding model, hence there was some deviation in the results of the experiment.

Development of the Rutherford Model

Rutherford’s renowned gold foil experiment took place in 1909. Rutherford and his colleague Hans Geiger attacked a piece of gold foil with positively charged alpha particles, expecting the particles to pass straight through. Instead, many alpha particles ricocheted off the foil, indicating that these particles were colliding with something positive. This positive force nucleus was given a name.

Discovery of the Atom

Democritus, a Greek philosopher, was the first to conceive of the atom around 400 BCE. During Europe’s Dark Ages, the concept was forgotten until 1803, when British scientist John Dalton hypothesised that everything was made up of very little indivisible components called atoms.

Dalton’s simple atom model survived until 1897, when J.J. Thomson, another British physicist, discovered that atoms contained tiny negatively charged particles known as electrons. Between 1897 and 1909, scientists believed that atoms were made up of electrons evenly distributed over a positively charged matrix. The plum pudding model was created by J.J. Thomson.

The atom was shown as a tiny, solid, indivisible sphere in Dalton’s model. Electrons (green circles) are spread in a positively charged matrix in Thomson’s plum pudding model.

Observations of Rutherford Model Experiment

Rutherford came to the conclusion that based on the observations obtained throughout the experiment

• The majority of an atom’s space is vacant -alpha -particles went through the gold sheet in vast numbers without being deflected. As a result, the vast majority of an atom must be empty.
• The positive charge in an atom is not evenly distributed and is concentrated in a limited area – The gold sheet deflected a small number of -particles when they were blasted. As a result, he came to the following conclusion.
• Only a few alpha-particles had deflected back or deflected at enormous angles. Furthermore, just a few particles deflected at 180o. As a result, he determined that positively charged particles covered a little portion of an atom in comparison to negatively charged particles.

Postulates of Rutherford atomic model based on observations and conclusions

Positively charged particles make up an atom. The majority of an atom’s mass was contained in a very small area. The nucleus of an atom was named after this part of the atom. The very small and dense nucleus of an atom is made up of neutrons and protons, as was discovered later.

The nucleus of an atom is surrounded by electrons, which are negatively charged particles. The electrons travel in a fixed circular path around the nucleus at a very high speed. “Orbits” were given to these fixed circular pathways.

Because electrons are negatively charged and the tightly concentrated nucleus is positively charged, an atom has no net charge or is electrically neutral. The nucleus and electrons are held together by a strong electrical attraction.

The nucleus of an atom is extremely small when compared to the whole size of the atom.

Limitations of Rutherford Atomic Model

Certain aspects of Rutherford’s experiment were unable to be explained. They are as follows:

The stability of an atom was not explained by Rutherford’s idea. According to Rutherford’s assumption, electrons in a fixed orbit rotate at a very high speed around the nucleus of an atom. Maxwell, on the other hand, explained that accelerated charged particles emit electromagnetic radiations. Electrons spinning around the nucleus will emit electromagnetic radiation as a result.

The electromagnetic radiation will gain energy from the electrical action, causing the orbits to shorten over time. In the nucleus of an atom, the orbits will eventually shorten and collapse.  As a result, the Rutherford atomic model did not follow Maxwell’s theory and was unable to explain the stability of an atom.

Rutherford’s idea was flawed because it omitted information on the electron arrangement in the orbit. One of the key flaws in the Rutherford atomic model was this.

Conclusion

Despite the fact that early atomic models were erroneous and unable to adequately explain the structure of the atom and experimental results. However, it served as the foundation for quantum mechanics and aided in its future growth.