H2O is the chemical formula for water. It is a molecule consisting of two hydrogen atoms bonded to one oxygen atom.
This term refers to ammonia, a compound made up of one nitrogen atom bonded with three hydrogen atoms.
CH4: This term represents methane, which consists of one carbon atom bonded with four hydrogen atoms.
CO2: This term stands for carbon dioxide—a molecule composed of one carbon atom double-bonded with two oxygen atoms.