Question

Who discovered the nucleus? Describe the experiment that led to this discovery.

Short answer

Answer: Ernest Rutherford is the scientist who discovered the nucleus of an atom. He conducted the gold foil experiment, where he fired alpha particles at a thin gold foil and observed their scattering patterns. The unexpected deflection of a small fraction of alpha particles led Rutherford to conclude that atoms have a small, dense, positively charged core called the nucleus.

Step-by-step solution

Identify the scientist

Ernest Rutherford is the scientist who discovered the nucleus of an atom.

Explain the purpose of Rutherford's experiment

Rutherford's objective was to probe the structure of an atom by studying how alpha particles, positively charged particles emitted by certain radioactive materials, scattered when fired at a thin gold foil.

Describe the experimental setup

Rutherford's experiment, known as the gold foil experiment, consisted of a radioactive alpha particle source, a thin gold foil, and a detector screen, which was a zinc sulfide screen that emitted tiny flashes of light when struck by alpha particles.

Explain the initial expectations

It was expected that the alpha particles would pass straight through the gold foil with minor deflections because the prevailing model, J.J. Thomson's plum pudding model, suggested that atoms had a diffuse positive charge distributed throughout a uniformly distributed mass, in which negatively charged electrons were embedded like raisins in plum pudding.

Describe the actual results of the experiment

Rutherford observed that while the majority of alpha particles passed straight through the gold foil with minor or no deflections, a small fraction of them surprisingly bounced back, sometimes at very large angles, as if they had struck something massive and positively charged within the atom.

Explain Rutherford's conclusions

Rutherford concluded that atoms must have a small, dense, positively charged core, which he called the nucleus. This explained why some of the alpha particles were heavily deflected, as they were repelled by the positively charged nucleus. The majority of the atom was empty space, allowing most alpha particles to pass straight through the gold foil with little or no deflection. This led to the development of the Rutherford atomic model, which replaced the plum pudding model.