Summary
Highlights
Before the discovery of electrons in 1897, atoms were thought to be indivisible spheres. The discovery of electrons led to the Plum Pudding model, where an atom was described as a ball of positive charge with negative electrons embedded within it.
To test the Plum Pudding model, scientists conducted the alpha scattering experiment. They fired positively charged alpha particles at a very thin gold foil. Most particles passed straight through, some were deflected, and a few bounced straight back.
The experiment's results revealed that atoms are mostly empty space, the center of an atom has a positive charge, and this central part contains most of the atom's mass. This led to the development of the nuclear model, where a tiny, dense, positively charged nucleus is at the atom's center, with electrons orbiting in mostly empty space.