3.5 acid acidic alcohol allotropy aluminum argon arsenic atomic number barium beryllium bond boron brass calcium carbon catalyst chemical chlorine complex concentration copper electron configuration electronic element fluorine gold helium hydrogen iodine iron isotope krypton lead lithium magnesium manganese mercury neon nickel nitrogen oxidize oxidized oxygen periodic table phosphorus platinum plutonium potassium product protactinium radical radium saturated saturation scandium silicon silver sodium spectrum steel strontium sulfur tin unoxidized unsaturated uranium water zinc