Quantum numbers: - Principal quantum number ($n$): Shell (1, 2, 3, ...) - Azimuthal quantum number ($l$): Subshell (s, p, d, f for $l=0, 1, 2, 3$ respectively) - Magnetic quantum number ($m_l$): Orbital orientation ($ -l, ..., 0, ..., +l $) - Spin quantum number ($m_s$): Electron spin ($ +1/2 $ or $ -1/2 $) The orbital notation is given by $n$ followed by the subshell letter (e.g., 1s, 2p, 3d).