The answer is Oxygen. Oxidizeris a powerful, it deodorizes water and kills germs at concentrations of 1 part per million. At even lower concentrations in air it causes coughing, chest pain, and eye irritation. This reaction occur over and over again, let a single atom of chlorine to act as a catalyst, it will affects many molecules of ozone. Experiments show its molecular structure exhibits resonance, as the oxygen-oxygen bonds are both identical. For ten points, identify this poisonous blue gas, whose molecules each contain three atoms.