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From The Chemistry Book
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Joseph John Thomson (J.J. Thomson) published his discovery of the first subatomic particle, called the electron, in 1897. The discovery was an outcome from a series of experiments in which he studied the nature of electric discharge in a high-vacuum cathode-ray tube (CRT).
Plum pudding model
J.J. Thomson abandoned his earlier vortex model and developed an atomic model in which he described negatively charged electrons scattered in a sphere shaped atom. Because the atom is not charged, he suggested positively charged sphere around the atom. The positive charges were not scattered throughout and the protons were not discovered yet.
The 1904 model is named the plum pudding model. This model is in stark contrast to the Greeks' and John Dalton's model, suggesting the atom was a solid sphere.