`electron_config(26)` returns `"[Ar] 3d^6 4s^2"` (iron) - `term_symbols(2, 1)` returns `['1S_0', '3P_2,1,0', '1D_2']` (carbon $p^2$) - `hund_ground_state(...)` selects ${}^3P_0$ for carbon - `hartree_helium(2)` converges to $E \approx -77.9\;\text{eV}$ (Hartree--Fock limit for He)