Plum Pudding Model
J. J. Thomson's 1904 model picturing the atom as a sphere of diffuse positive charge with electrons embedded within it.
Unit
Dimensionless
In depth
It was the first model to include subatomic particles, following Thomson's discovery of the electron in cathode rays. Since positive charge was spread through the whole atom, the model predicted only small deflections of alpha particles, and the gold foil experiment decisively refuted it.
Examples in the real world
Thomson's model made the alpha-scattering result inexplicable, forcing the nuclear picture that replaced it.