Rutherford's α-particle scattering experiment shows that :
(i) electrons have negative charge.
(ii) the mass and positive charge of the atom is concentrated in the nucleus.
(iii) neutron exists in the nucleus.
(iv) most of the space in atom is empty.
Which of the above statements are correct ?

Question

Rutherford's α-particle scattering experiment shows that :
(i) electrons have negative charge.
(ii) the mass and positive charge of the atom is concentrated in the nucleus.
(iii) neutron exists in the nucleus.
(iv) most of the space in atom is empty. 
Which of the above statements are correct ?

Accepted Answer

Rutherford's α-particle scattering experiment was a groundbreaking experiment that led to significant insights into the structure of the atom. Let's analyze why Option 2, which includes statements (ii) and (iv), is the correct answer, and why the other options are incorrect.

### Explanation Supporting Option 2:

1. **Statement (ii): The mass and positive charge of the atom is concentrated in the nucleus.**
   - Rutherford's experiment involved directing a beam of α-particles at a thin gold foil. He observed that most of the α-particles passed through the foil with little or no deflection, but a small fraction were deflected at large angles, and some even bounced back. This led to the conclusion that the atom's positive charge and most of its mass are concentrated in a small, dense region called the nucleus. This nucleus is positively charged because it repels the positively charged α-particles.

2. **Statement (iv): Most of the space in the atom is empty.**
   - The observation that most α-particles passed through the gold foil without deflection indicates that atoms are mostly empty space. The nucleus occupies a very small volume compared to the entire atom, allowing the α-particles to pass through the empty space without encountering any significant obstacles.

### Explanation for Why Other Options are Incorrect:

1. **Option 1: (ii), (iii), and (iv)**
   - **Statement (iii): Neutron exists in the nucleus.**
     - Rutherford's experiment did not provide evidence for the existence of neutrons. Neutrons were discovered later by James Chadwick in 1932. Therefore, including statement (iii) makes this option incorrect.

2. **Option 3: (i), (ii), and (iv)**
   - **Statement (i): Electrons have negative charge.**
     - While it is true that electrons have a negative charge, Rutherford's experiment did not directly address the charge of electrons. The experiment focused on the nucleus and the distribution of mass and charge within the atom. Therefore, statement (i) is not relevant to the conclusions drawn from Rutherford's experiment, making this option incorrect.

3. **Option 4: (i) and (iii)**
   - As explained above, statement (i) is not directly related to Rutherford's experiment, and statement (iii) is incorrect because the experiment did not provide evidence for neutrons. Therefore, this option is incorrect.

In conclusion, Option 2 is the correct answer because it accurately reflects the conclusions drawn from Rutherford's α-particle scattering experiment: the concentration of mass and positive charge in the nucleus and the fact that most of the atom is empty space.