Rutherford Atomic Model: Postulates, Experiment, Facts And Drawbacks

We explain to you what Rutherford’s atomic model is and its main postulates. Also, how was the Rutherford experiment.

What is the atomic model of Rutherford?

Rutherford’s atomic model, as the name implies, was the theory regarding the internal structure of the atom proposed in 1911 by British chemist and physicist Ernest Rutherford, based on the results of his experimentation with gold foils.

This model constituted a break with previous models such as the Thompson Atomic Model, and a step forward from the currently accepted model.

In his atomic model , Rutherford proposed that the atoms would have a central nucleus where the greatest percentage of their mass falls , endowed with a positive electrical charge, and that it was orbited by particles of opposite charge and smaller size.

According to their considerations, the atom operated as a solar electron system orbiting a heavier atomic nucleus, as planets around the Sun do.

Rutherford’s atomic model can be summarized in the following three propositions:

  • Most of the atomic mass is concentrated in the nucleus, larger and heavier than the rest of the particles, and equipped with a positive electrical charge.
  • Around the nucleus and to great distances of him there are the electrons, of negative electrical charge, orbiting it in circular trajectories.
  • The sum of the positive and negative electric charges of an atom should result in zero, that is, they should be equal, so that the atom is electrically neutral.

Rutherford not only proposed this structure, but also calculated its size and compared it with the size of the nucleus, concluding that a good part of the composition of the atom is empty space .

The atomic model of Rutherford was in force for a short time, being replaced by the atomic model proposed by Danish physicist Niels Bohr in 1913, in which the theoretical proposals developed by Albert Einstein in 1905 were incorporated.

Rutherford’s experiment

Rutherford’s experimental method was based on several thin sheets of gold that would be bombarded in the laboratory with helium nuclei (alpha particles), thus measuring the deflection angles of the particle beam as gold passed through.

This behavior, which sometimes reached deviations of up to 90 °, did not match the atomic model proposed by Thompson, prevailing at the time, according to which the atoms were diffuse clouds, positively charged inside which had electromagnetically neutralized electrons . From these results, Rutherford was able to reformulate the idea of ​​the atom that was used until the time.

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