In Rutherford's experiment, some of the alpha particles got scattered through large angles. Consider the following reasons.

1. Atom has a positively charged core in the centre.

2. The positive charges are not uniformly distributed inside the atom.

3. Alpha particles are fast-moving particles.

Which among the above statements is/are correct?

The correct answer is 1 and 2 only.

EXPLANATION:

• Rutherford conducted an experiment by bombarding a thin sheet of gold with α-particles and then studied the trajectory of these particles.
• The key findings of the experiment-
  • A major fraction of the α-particles passed through the sheet without any deflection, and hence most of the space in an atom is empty.
  • Some of the α-particles were deflected by very small angles, and hence the positive charge in an atom is not uniformly distributed.
  • A very few of the α-particles were deflected back at nearly 180⁰ angle, so the volume occupied by the positively charged particles in an atom is very small as compared to the total volume of an atom. (statement 2 is correct)
• Rutherford deduced that the positive charge in an atom is concentrated into a small compact nucleus and hence most of the mass is also situated at the center. (statement 1 is correct)

Key Points

• Please note that the nucleus of the atom contains protons (positively charged) and neutrons (neutral charged).
• Since the alpha particles are also positively charged,  it gets deflected (repulsed) by the nucleus at large angles.
• Statement 3 is independent of the scattering of alpha particles through large angles. Hence, it cannot be the reason for deflection. (statement 3 is incorrect for this question)