Rutherford's scattering experiment:

Rutherford's model of an atom :

Ernest Rutherford was interested in knowing how the electrons are arranged within an atom.Rutherford designed an experiment for this. In this experiment, fast moving alpha (α)-particles were made to fall on a thin gold foil.

He selected a gold foil because he wanted as thin a layer as possible. This gold foil was about 1000 atoms thick.

α-particles are doubly-charged helium ions. Since they have a mass of 4µ, the fast-moving α-particles have a considerable amount of energy.

It was expected that α-particles would be deflected by the sub-atomic particles in the gold atoms. Since the α-particles were much heavier than the protons, he did not expect to see large deflections.But, the α-particle scattering experiment gave totally unexpected results .

Observations of Rutherford's scattering experiment:

As we can see in Fig.

Most of the fast moving α-particles passed straight through the gold foil.

Some of the α-particles were deflected by the foil by small angles.

Surprisingly one out of every 12,000 alpha particles appeared to rebound.

Conclusion of Rutherford's scattering experiment:

Most of the space inside the atom is empty because most of the α-particles passed through the gold foil without getting deflected.

Very few particles were deflected from their path, indicating that the positive charge of the atom occupies very little space.

A very small fraction of α-particles were deflected by very large angles, indicating that all the positive charge and mass of the gold atom were concentrated in a very small volume within the atom.