The Free Electron Model was created back in the year 1927 by Arnold Sommerfeld. This model is said to have stemmed from different models. This model was created in order to describe how electrons possibly work in solid metals. This is a very simple model and yet it was able to explain some natural phenomena that people at that time were not able to explain.
It shows how thermal and electrical conductivity may potentially take place. It also shows how the particles of atoms are sometimes dependent on temperature and will be affected by it. The shape of the electronic density can also be explained by this model. It has truly answered some questions at that time.
It was in the year 1897 when free electrons were first discovered by J.J Thompson. He was just looking into the properties of the cathode ray when he made the discovery. The moment that free electrons were discovered, people looked into it and it immediately became a big deal. By the year 1900, there was already a theory made about this.
This electron theory is related to the thermal and electrical conduction in metals. There were still a few changes made to this theory by Lorentz a few years later. This was a theory that was believed in until the year 1928. By then, there were already more theories that were made that are related to free electrons.