Scientists sometimes replace one scientific model with a different model - AQA - GCSE Physics - Question 2 - 2018 - Paper 1

The transition from the plum pudding model to the nuclear model of the atom occurred due to several key experimental findings:

1. Alpha Particle Scattering Experiment: In the early 1900s, Ernest Rutherford conducted the alpha particle scattering experiment, where alpha particles were directed at a thin gold foil.

2. Observation of Deflections: Rutherford observed that most alpha particles passed straight through the foil, suggesting that the majority of the atom's volume is empty space.

3. Significant Deflections: A small number of alpha particles were deflected at large angles, indicating the presence of a concentrated mass within the atom.

4. Conclusion about Atomic Structure: These observations led to the conclusion that atoms consist of a dense, positively charged nucleus at the center, surrounded by electrons, fundamentally contradicting the plum pudding model, which posited that electrons were distributed evenly throughout a positively charged 'soup'.

5. Charge Distribution: In the nuclear model, the mass is concentrated in the nucleus, which accounts for the atom's mass and charge, whereas the plum pudding model did not adequately explain the observations of charge and mass distribution within atoms.

Through these experiments, the nuclear model provided a more coherent and accurate representation of atomic structure.