Physics 2020 JAMB Past Questions - Question 40: In the Rutherford scattering experiment, a beam of alpha particles was fired at a thin gold film with some of the particles being considerably deflected. This shows that

Correct Answer

B

Explanation

 The Rutherford scattering experiment was a crucial experiment conducted by Ernest Rutherford in 1909 that provided strong evidence for the existence of a small, dense atomic nucleus. In this experiment, a beam of alpha particles (helium nuclei) was directed at a thin gold foil.

The prevailing model of the atom at the time was the Thomson or "plum pudding" model, which suggested that the positive charge in an atom was uniformly distributed throughout the atom, with negatively charged electrons embedded in it like plums in a pudding. According to this model, it was expected that the alpha particles would pass through the gold foil with minimal deflection.

However, what Rutherford observed was quite different. While most of the alpha particles did pass through the foil with little deflection, some were significantly scattered at large angles, and a few even bounced back in the direction from which they came. This unexpected result led Rutherford to propose a new atomic model.

The significant deflection of some alpha particles in the experiment indicated that the positive charge in the atom was not uniformly distributed but was concentrated in a small, dense nucleus at the center of the atom. The rest of the atom, mostly empty space, allowed most alpha particles to pass through undeflected.

This discovery revolutionized the understanding of the atom and laid the foundation for the development of the modern atomic model, where electrons orbit a central nucleus. Rutherford's model was later refined with the incorporation of quantum mechanics, but the basic idea of a small, dense nucleus remained.