CBSE Class 9 Answered

In 1911, Earnest Rutherford, a scientist from New Zealand, overturned Thomson’s atomic model by his gold foil experiment.

• Rutherford selected a gold foil as he wanted a very thin layer.
• The gold foil used by Rutherford was 0.004 millimetres in thickness. That is, the foil was about 1000 atoms thick.
• In his experiment, fast moving α-particles (alpha particles) were made to fall on a thin gold foil.
• The α-particles are helium ions with a +2 charge. Their atomic mass is 4 u. Hence, a high velocity beam of α-particles has a lot of energy.  
• These particles were studied by means of flashes of light they produced on striking a zinc sulphide screen.
• The α-particles are much heavier than the sub-atomic particles present in gold atoms.
• Hence, he expected the α-particles to pass through the gold foil with little deflection and strike the fluorescent screen.

  Answered by | 30 Mar, 2016, 07:51: PM