Thomson Atomic Model


Thomson’s atomic model is a theory that talks about the structure of atoms, it was proposed by the British physicist Joseph Thomson, who is also the discoverer of the electron. Through this model, Thomson affirmed that the positively charged atom was made up of negative electrons, which were embedded in it, as if they were raisins in a pudding. Because of this comparison, this atomic model is also known as the “raisin pudding model.”

Thomson’s model stated that the electrons were uniformly distributed in the internal part of the atom fixed in a cluster of positive charge. The atom was seen as a sphere full of positive charge, with electrons scattered as tiny granules.

Thomson’s theory determined:

  • The atom is made up of negative electrons, introduced into a balloon of positive charge, just like a raisin pudding.
  • Electrons are evenly distributed within the atom.
  • The atom is neutral, therefore, its negative charges are offset by positive charges.

The theory proposed by Thomson, although it favorably showed several of the observed events related to chemistry and cathode rays, made erroneous predictions about the distribution of positive charge within atoms. These predictions were not compatible with the results of the Rutherford model, which proposed that the positive charge was condensed in a small area in the center of the atom, which would be what was later called the atomic nucleus.

Thomson’s model was replaced by Rutherford’s, as it was shown that the latter is not compact, but is completely empty, with the positive charge being grouped in a small nucleus, surrounded by electrons.