Air is composed primarily of nitrogen (78.09%) and oxygen (20.95%) but also contains smaller amounts of argon (0.93%), carbon dioxide (0.03%) and trace amounts of other gases. While oxygen is an important component of air, saying air is just oxygen is incorrect as it contains several other significant gases besides oxygen.
13. Thanks to the following websites for helpful information and graphics: http://www.google.com/imgres?imgurl http://education.jlab.org/glossary/abund_atmos.html http://commons.wikimedia.org/wiki/File:Carbon-dioxide-2D-dimensions.png