By trying to understand the structure of matter one has always the feeling that the nature could be explained in terms of building blocks, which join together or break apart in simple ways. The Greeks thought that there might be basic atoms, out of which everything else could be formed.
Over the years this ancient philosophical approach led scientists to several theories. However, only in 1900 when Max Planck postulated his quantum hypothesis, scientists had a mathematical basis for establishing the modern atomic theory and ultimately for explaining the behavior of electrons in solids.
In 1926, another German physicist Erwin Schrodinger formulated the famous quantum mechanical equation, which could quantify the behavior of electrons in solids. Fig 247
By using those scientifics advancements after almost 50 years of its discovery physicists finally could tiedty together all the puzzling phenomena found in the crystal detection, led to the birth of the first man-made semiconductor device.
Fig. 247 - a didactic concept of the structuring of an atom according the suggestion proposed by Niels Bohr in 1940, displaying the electron configuration of the Boron element. The elemental atom's particle comprising the nucleous with 5 protons and 5 neutrons as well as the outer orbit with 5 electrons. Nowadays, more accurate mathematical model are used because the particle path, for instance the electron's position, cannot be measured so accurately to justify picturing it in an orbit around the nucleous. The mathematical formulation can forecast the probability of finding the electron at different distances from the nucleous. This vaguenes about electronic configuration is the physicists' saga when discribing the behavior of atom particles.

Planetary eletrons in orbit. Composed nucleus for 5 protons and 5 neutrons.