Topic overview

Start with the big picture

The lesson begins with the Aufbau principle, the Pauli exclusion principle, and Hund’s rule as foundations for assigning electrons to orbitals. It then explains how the four quantum numbers describe single-electron states and how shielding and penetration influence sublevel energies and effective nuclear charge. For many-electron states, the topic introduces term symbols and LS and jj coupling, alongside antisymmetric wavefunctions and Hartree–Fock approximations. Further sections address correlation, quantitative corrections such as Slater rules and quantum defects, and the links between electron configuration and periodic trends. The broader structure also covers fine and hyperfine structure, relativistic effects, configuration interaction, and restrictions on optical transitions.