Atom Orbital Simulator Atom Orbital Simulation (1–18) Atomic Number (Z): 1 – Hydrogen 2 – Helium 3 – Lithium 4 – Beryllium 5 – Boron 6 – Carbon 7 – Nitrogen 8 – Oxygen 9 – Fluorine 10 – Neon 11 – Sodium 12 – Magnesium 13 – Aluminium 14 – Silicon 15 – Phosphorus 16 – Sulfur 17 – Chlorine 18 – Argon