In details

Thomson's model

Dalton's model made it possible to explain various phenomena and contributed greatly to the evolution of knowledge of matter. However, it did not consider the electrical nature of matter.

Electricity had been studied since the eighteenth century, and scientists were advancing new research and experiments. The theory concerning the existence of a particle of negatively charged matter, the electron, was consolidated.

New knowledge, new questions were asked, and Dalton's model did not satisfy, as it did not explain the existence of the electron. It was necessary, then, a model that was based on the fact that matter, therefore the atom, has particles with a negative electric charge and supposedly also contains particles with a positive electric charge.

About a century after Dalton, the English scientist Joseph John Thomson He proposed another model to explain the atom, taking into account existing knowledge about electricity.

In 1887, Thomson stated that the atom would be a neutral, massive, nonhomogeneous sphere composed of a positive fluid in which electrons would be scattered.

In the Thomson model, the atom continues to be represented by a tiny massive sphere, but reveals the atom as a complex and divisible structure.

This model of atom is called by some of “Raisin pudding”: the pudding mass would be the positive charge, and the raisins scattered over the pudding would be the negative particles - the electrons.

The discovery and studies of radioactivity, as well as significant technological advances, led scientists to further speculation about the composition of matter and the structure of the atom.