Respond to the following questions.
A scientist compared hydrogen and helium. Hydrogen has one proton. Helium has two protons. However, helium has about four times the mass of hydrogen.
This puzzled scientists because protons alone could not explain such a large increase in mass. They realised that another particle must exist inside the nucleus. Later, James Chadwick discovered the neutron.
1. Which statement about the discovered particle is correct?
2. A nucleus contains four particles, of which only two contribute to its positive charge. What can be concluded?