Rutherford atomic model was the first step in the evolution of the modern atomic model. Ernest Rutherford was a keen scientist who worked to understand the distribution of electrons in an atom. He performed an experiment using alpha particles and gold foil and made the following observations:
- Most of the alpha particles passed straight through the gold foil.
- There was a deflection of the alpha particles by a small angle.
- Very small amount of alpha particles rebounded.
From his experiment, he came to following conclusions:
- Most of the space in an atom is empty.
- The space occupied by the positive charges is very small.
- The positive charges and mass of the atom were concentrated in a very small volume within an atom.
From these conclusions, he calculated that the radius of the nucleus is around 105 times less than that of the atom.
Rutherford Atomic Model
Rutherford developed a nuclear model of atom on the basis of his experiment and observations. The Rutherford atomic model has the following features:
- The centre of an atom is called nucleus. It is positively charged and almost all mass of the atom resides in it.
- Electrons spin around the nucleus in a circular path.
- Comparatively, the size of the nucleus is smaller than the size of the atom.
Drawbacks of Rutherford Atomic Model
As before, Rutherford atomic model was also challenged and questioned by many. Rutherford atomic model failed to explain about the stability of electrons in a circular path.
As per Rutherford’s model, electrons revolve around the nucleus in a circular path. But particles that are in motion on a circular path would undergo acceleration, and acceleration causes radiation of energy by charged particles. Eventually, electrons should lose energy and fall into the nucleus. And this points to the instability of atom. But this is not possible because atoms are stable. Hence, Rutherford failed to give an explanation on account of this.
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