Question

Why was the presence of neutrons in an atom predicted? How were neutrons discovered?

Answer 1

1. The $\mathrm{\alpha }$ particles are heavy positively charged particles, they can be deflected only if they come close to some heavy positively charged mass within the atom.
2. Rutherford called this positive center as the nucleus.
3. It was Chadwick who bombarded a thin sheet of beryllium with fast-moving $\mathrm{\alpha }$ particles.
4. He found that some new particles were emitted that carried no charge but had a mass nearly equal to that of a hydrogen atom.
5. These particles were named neutrons.