In 1911, Rutherford carried out experiments on the bombardment of the atoms by high speed positively charged α-particles. He struck (bombarded) thin metallic sheet of gold (0.00004 cm thick) with a-particles emitted from radium and observed that :
(i) majority of α-particles continued their straight path.
(ii) some which passed very close to the centre of the atom were deflected from their path through large angles.
(iii) and very few were thrown back.
The above experiment led Rutherford to conclude the following facts :
(a) The atom is largely empty space, since most of the α-particles pass straight through the atom.
(b) The centre of the atom has a positively charged body called nucleus to repel positively charged a-particles and thus explains the scattering of a-particles.
(c) The whole of the atomic mass is concentrated in the nucleus i.e. the central nucleus is rigid and hence α-particles, which strike on it, are thrown back. Moreover, since very few α-particles are deflected back, the size or volume of the nucleus must be very small as compared to the total size or volume of the atom.
