Chapter 9: The Periodic Table and Some Atomic Properties

The Periodic Table and Some Atomic Properties provides an in-depth educational exploration of the periodic table and the foundational atomic properties that govern chemical behavior and reactivity. It traces the historical development of the periodic law from Mendeleev and Meyer to Moseley's modern arrangement based on atomic number, establishing the essential framework for categorizing elements into metals, nonmetals, metalloids, main-group elements, and transition metals. A central focus is placed on the relationship between ground-state electron configurations and the formation of ions, detailing how main-group elements strive for stable noble gas configurations while transition metals exhibit unique ionization patterns by losing outer s-orbital electrons before d-orbital electrons. The text systematically unpacks critical periodic trends involving atomic and ionic radii—encompassing covalent, metallic, and van der Waals measurements—heavily emphasizing the role of effective nuclear charge, electron shielding, and orbital penetration in dictating atomic size across periods and down groups. Furthermore, the chapter rigorously analyzes ionization energy and electron affinity, explaining the energetic thermodynamic principles behind electron removal and addition, alongside notable expected deviations driven by electron-electron repulsions and subshell stability. The discussion extends to the magnetic properties of atoms and ions, distinguishing between diamagnetic species with entirely paired electrons and paramagnetic species characterized by unpaired electrons that are attracted to external magnetic fields. Finally, the concept of polarizability is introduced, illustrating how the physical distortion of an atom's electron cloud correlates with atomic volume and valence electron binding, thereby laying the crucial groundwork for understanding chemical bonding, intermolecular forces, and molecular reactivity.