2 Molecules of Oxygen O2 Element, Compound, or Mixture? www.middleschoolscience.com 2016 1 Molecule of Methane CH4 3 Molecules of Methane and Oxygen O2 2 Molecules of Water H2O 18 Atoms of Sodium Na 4 Molecules of Sodium Chloride NaCl, Carbon Dioxide CO2 & Water H2O 2 Molecules of Hydrogen H2 3 Molecules of Sodium Chloride NaCl 4 Molecules of Water H2O and Oxygen O2 3 Molecules of Nitrogen N2 5 molecules of Nitrogen N2 and Cl2