Question

The main substances in air are N2 (nitrogen), O2 (oxygen), CO2 (carbon dioxide), H2O (water), and Ar (argon). Which of these substances are elements? Which are compounds? Which are molecules?

Answer 1

Ar is elements. H2O and CO2 are compounds. H2O and CO2 and O2 and N2 and Ar are also regarded as molecules.

Answer 2

78% nitrogen, 21% oxygen and 1% other gases

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