This lecture delves into the behavior of electrons beyond conductivity, exploring thermophysical properties, solid solubility, and Hume-Rothery rules. It discusses the multitude of phase diagrams, the differences in behavior between 3d, 4d, and 5d shell filling rows, and the characteristics of Hume-Rothery phases. The lecture also covers the Kubaschewski diagram, solid solubility rules by Darken and Gurry, and the theory of Hume-Rothery phases by Mott & Jones. Additionally, it extends to ternary phase diagrams and the structure of y-brass and ordered y'.