Rutherford designed an experiment to know about the arrangement of electrons within an atom. He took a gold foil on which the fast-moving alpha particles were made to fall. He took a very thin layer of gold foil which was about 1000 atoms thick.

Rutherford concluded the following from the α-particle scattering experiment:

(i) Most of the alpha particles passed through the gold foil without getting deflected. This concluded that most of the space inside the atom is empty. This observation was totally unexpected.

(ii) Some of the α-particles were deflected by the foil by small angles. The number of particles which were deflected was very small. This shows that the positive charge of the atom occupies very little space.

(iii) Surprisingly one out of every 12000 particles appeared to rebound meaning they were deflected by 180 degrees. This concluded that all the positive charge and the mass of the atom were concentrated in a very small volume within the atom.

From the data, he also calculated that the radius of the nucleus is about 105 times less than the radius of the atom. Based on this data Rutherford put forward the model of an atom which had a positively charged center called nucleus. It also had the electrons which revolved around the nucleus in well defined orbits.