Scientists sometimes replace one scientific model with a different model - AQA - GCSE Physics - Question 10 - 2018 - Paper 1

The transition from the plum pudding model to the nuclear model of the atom was significantly influenced by the results of the alpha particle scattering experiment conducted by Ernest Rutherford in 1909. In this experiment:

1. Alpha Particle Scattering Experiment: Alpha particles were directed at a thin gold foil. According to the plum pudding model, which suggested that atoms were a diffuse cloud of positive charge with electrons embedded within, it was expected that most alpha particles would pass straight through the foil with minimal deflection.

2. Observation of Deflections: However, the results were surprising. While most alpha particles did pass straight through, a small fraction were deflected at large angles, and some even bounced back toward the source.

3. Conclusions Drawn: This unexpected behavior indicated that a small, dense, positively charged nucleus must exist within the atom, containing most of its mass, while the rest of the atom was largely empty space. This contradicted the plum pudding model, which could not adequately explain the observations.

4. Characteristics of the Nucleus: The nucleus was identified as being positively charged and concentrated at the center of the atom. This implied that electrons orbited around this central nucleus, leading to the formation of the nuclear model.

Thus, the empirical evidence from Rutherford's experiment highlighted the inadequacies of the plum pudding model and paved the way for the nuclear model, which was better supported by experimental data.