Final answer:
James Chadwick's experiment involved bombarding beryllium with alpha particles to discover the neutron, which has similar mass to protons but is uncharged, resolving inconsistencies in the atomic model and earning him a Nobel Prize.
Step-by-step explanation:
The experiment conducted by James Chadwick to develop his model involved the bombardment of beryllium with alpha particles. This was initially conducted by German researchers who observed that an unknown radiation was emitted, which did not bend under magnetic or electric fields, suggesting it was not charged. Chadwick's hypothesis was that this radiation consisted of particles with a mass similar to protons but without charge—neutrons. He measured the velocities of these particles to determine their mass and found it to be comparable to that of protons. This discovery was crucial in advancing the atomic model, as it accounted for the discrepancy between the number of protons in an atomic nucleus and its atomic weight. Chadwick's findings led to him being awarded the Nobel Prize in Physics in 1935.