This episode dives into atomic structure and periodicity, focusing on how the arrangement of electrons within an atom impacts various chemical properties. It begins by introducing fundamental concepts like Coulomb's Law, electrostatic potential energy, and the photoelectric effect, explaining how these factors influence the behavior of electrons in atoms. Then we examine photoelectron spectroscopy (PES) as a method to measure ionization energies and deduce the shell structure of atoms. We further dive into electron configurations, connecting them to the patterns observed in PES data and illustrating how they correlate with the periodic table. Finally, episode explores the trends in ionization energy, atomic and ionic radii, and electronegativity, providing explanations for these patterns based on effective nuclear charge and Coulomb's Law.