Answer Exercise 3.14 concerning the discovery of neutrons.

Here are the answers to .14:

1. Who discovered the neutrons?

   • Answer: James Chadwick

2. Neutrons were discovered by bombarding beryllium with alpha particles.

3. Why the presence of the neutrons in an atom was predicted?

   • Answer: The presence of neutrons was predicted because the atomic mass of most elements was greater than the total mass of their protons alone. This suggested that there must be another particle in the nucleus contributing mass but no electrical charge. Ernest Rutherford had earlier hypothesized the existence of such a neutral particle.

4. How were the neutrons discovered?

   • Answer: Neutrons were discovered by James Chadwick in 1932. He bombarded a thin sheet of beryllium with alpha particles. This interaction produced a highly penetrating, uncharged radiation. When this radiation hit paraffin wax, it ejected protons. By analyzing the energy of these ejected protons, Chadwick deduced that the uncharged radiation was composed of particles with a mass similar to that of a proton, which he named neutrons.