Atomic Structure
Development of the Atomic Model
To describe how scientific discoveries changed our understanding of the atom, from early models to the modern nuclear model.
What you will learn
How scientists’ ideas about atoms have changed
What Dalton and Thomson proposed about atoms
How Rutherford’s experiment revealed the nucleus
How Bohr improved the model of electron arrangement
How Chadwick’s discovery completed the nuclear picture
Explanation
Alpha scattering replaced the plum-pudding model with a small, dense, positive nucleus. Bohr refined the model with electrons at specific distances or energy levels; absorption raises an electron’s level and emission lowers it. Chadwick provided evidence for neutrons in the nucleus. New evidence changes scientific models when previous explanations cannot account for observations. Example: Explain why most alpha particles passed through foil. Most of the atom is empty space. Check your reasoning.