Question

Which experiment led to discovery of nucleus?

Answer 1

Rutherford Gold foil experiment showed the first experimental evidence that led to the discovery of the nucleus.

• In the experiment, Rutherford showed us that the atom was mainly empty space with the nucleus at the centre and electrons revolving around it.
• When alpha particles were fired towards the gold foil, Rutherford noticed that 1 in 20000 particles underwent a change in direction of motion of more than 90 degrees. The rest 19999 particles deviated from their trajectory by a very small margin.
• This led to the conclusion that the atom consisted of an empty space with most of the mass concentrated at the centre in tiny volumes. This volume at the centre was named the nucleus.

Through this experiment, Rutherford made 3 observations as follows:

• Highly charged alpha particles went straight through the foil undeflected. This would have been the expected result for all of the particles if the plum pudding model was correct.
• Some alpha particles were deflected back through large angles.
• A very small number of alpha particles were deflected backwards! To this Rutherford remarked, “It was as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back at you!”

To explain these observations, a new model of the atom was needed. In the new model, the positive material was considered to be concentrated in a small but massive region called the nucleus.