Development of the Atomic Model

Understand that newly acquired experimental evidence can directly lead to an established scientific model being systematically changed or entirely replaced.

Describe the early historical model of atoms, prior to the discovery of the electron, as tiny spheres that could not be fundamentally divided.

Explain how the discovery of the electron directly led to the formulation of the plum pudding model of the atom.

Describe the plum pudding model as suggesting the atom is a continuous ball of positive charge with individual negative electrons embedded within it.

Analyze how results from the alpha particle scattering experiment led to the definitive conclusion that atomic mass was concentrated at the centre, forming a charged nucleus.

Understand how this new nuclear model fundamentally replaced the previous plum pudding model.

Describe Niels Bohr's critical adaptation of the nuclear model, suggesting that electrons explicitly orbit the nucleus at specific, set distances.

Understand how Bohr's theoretical calculations closely agreed with observed experimental data.

Explain how later experiments led to the established idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, named protons.

Describe James Chadwick's experimental work, occurring roughly 20 years after the nucleus became accepted, which provided the vital evidence to prove the existence of neutrons within the nucleus.

Explain strictly why the new experimental evidence from the scattering experiment explicitly forced a change in the accepted atomic model.

Compare and clearly explain the fundamental differences between the plum pudding model of the atom and the nuclear model of the atom.