Question

Rutherford's scattering experiment is related to the size of the:
(A) Nucleus
(B) Atom
(C) Electron
(D) Neutron

Answer 1

Hint: Rutherford was originally interested in finding how the electrons are arranged inside an atom. Therefore, he performed an experiment for this, commonly known as alpha particle scattering. In his experiment, he made fast moving alpha particles to fall on a very thin gold foil.

Complete step by step solution:
Model for the structure of an atom had been first proposed by J.J. Thomson, commonly known as watermelon or plum pudding model. Later, Ernest Rutherford's model was finally accepted as the correct nuclear model.
Requirements of Rutherford's scattering experiment:
(i) He selected gold foil because it is very ductile, the thickness of the foil used was about 1000 atoms.
(ii) α-particles are doubly-charged helium ions. They have a mass of 4µ, so they can move very fast with a considerable amount of energy.
Rutherford expected that all the alpha particles would be deflected by the particles present in the gold atoms, since the alpha particles were much heavier than the protons. But the experiment gave completely different results.
Observations of Rutherford's scattering experiment:
(i) Most of the fast-moving alpha particles went straight through the gold foil without any deflection.
(ii) Some of the alpha particles were deflected by small angles.
(iii) Surprisingly, one out of every 12,000 alpha particles were completely reflected back.
From these observations, he concluded that:
(i) Most of the space inside the atom is vacant as most of the alpha particles went straight through the gold foil without any deflection.
(ii) A few particles showed little deflection from their trajectory, indicating that the positive charge of the atom occupies very small space.
(iii) And a very small number of alpha particles were deflected by very large angles or completely deflected back, indicating that all the positive charge and mass of the gold atom occupied a very small volume within the atom.
From the observation, Rutherford calculated that the radius of the nucleus, which was about \[{{10}^{5}}\] times less than the radius of the atom.

So, the correct option is (a).

Note: Rutherford's model could not explain the stability of an atom. As he said that electrons revolving around the nucleus continuously should lose energy and will be pulled towards the nucleus, resulting in colliding with it.