20 Elements of the Periodic Table Hydrogen (H)Helium (He)Lithium (Li)Beryllium (Be)Boron (B)Carbon (C)Nitrogen (N)Oxygen (O)Fluorine (F)Neon (Ne)Sodium (Na)Magnesium (Mg)Aluminum (Al)Silicon (Si)Phosphorus (P)Sulfur (S)Chlorine (Cl)Argon (Ar)Potassium (K)Calcium (Ca)