Atlas of Fundamental Concepts

Balmer and Rydberg exposed regular spectral structure before quantum mechanics. Rutherford concentrated positive charge in the nucleus; Bohr captured hydrogen’s gross spectrum; the Schrödinger equation replaced orbits with states and orbitals. Quantum numbers, exclusion, shells, and configurations organize many-electron atoms, while Hartree, Hartree–Fock, configuration interaction, coupled cluster, and density-functional theory provide computational frameworks with different approximation structures. Fine, hyperfine, Lamb, Stark, and Zeeman effects refine the spectrum.