Chemistry A-level 3.1.1 Atomic structure

John Dalton

• Early 1800s

• Hypothesised a model with solid spheres of different types

JJ Thomson

• 1897, ball of positive charge with small balls of negative charge embedded inside it

• Discovered electrons

Ernest Rutherford

• Made nuclear model with a positive small nucleus

• Rutherford scattering experiment, 1911

• Expected alpha particles to pass straight through gold foil but some deflected slightly and very few deflected at sharp angles or back to where they were fired, showing that there was a very small and concentrated area of positive charge, called the nucleus, and most passed straight through showing most of the atom was empty space

Niels Bohr

• 1913, discovered electrons orbit in shells at fixed distances

James Chadwick