Question

Rutherford’s alpha-particle scattering experiment was responsible for the discovery of
1. Atomic Nucleus
2. Electron
3. Proton
4. Neutron

Answer 1

Correct Answer - Option 1 : Atomic Nucleus

The correct answer is Atomic Nucleus.

• Rutherford's alpha-particle scattering experiment was responsible for the discovery of the atomic nucleus.
• Rutherford’s alpha-particle scattering experiment:
  • 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 4 u, 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. The following observations were made:
    • 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 12000 particles appeared to rebound
  • On the basis of his experiment, Rutherford put forward the nuclear model of an atom, which had the following features:
    • There is a positively charged centre in an atom called the nucleus. Nearly all the mass of an atom resides in the nucleus. 
    • The electrons revolve around the nucleus in circular paths.
    • The size of the nucleus is very small as compared to the size of the atom.

• Electron was discovered by J.J. Thomson in 1896.
• Sir James Chadwick discovered neutrons in the year 1932.
• The discovery of the proton is credited to Ernest Rutherford, who proved that the nucleus of the hydrogen atom (i.e. a proton) is present in the nuclei of all other atoms in the year 1917.