Science Challenge #5 Question 1. Which of the following elements (gases that occur normally in Earth's atmosphere) on a dry day makes up about 80% of the air we breathe? Argon, carbon dioxide, helium, hydrogen, krypton, neon, nitrogen, oxygen. (Our air also normally contains water vapor, hydrocarbons, hydrogen peroxide, sulphur compounds, in very small and variable amounts.) ANSWER: NITROGEN Correct responses received from: Peter Hance, Jennifer LeBlanc, Jack C., Jason Coffer, Lars, Sid Gospe, Jerome Rotch, Steve Liston