A quantum dot acts as an artificial atom. Electrons fill discrete shells (s, p, d…) following Hund's rules and Pauli exclusion. The addition energy (Coulomb blockade peaks) reveals shell structure with magic numbers 2, 6, 12…
Kouwenhoven et al. (1997): Coulomb blockade peaks in GaAs dots show shell structure. Magic numbers 2,6,12 for 2D harmonic confinement. Hund's rule: parallel spins fill degenerate levels first.