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Science

Chemical reactions and pollutants

When there is a chemical reaction, air pollutants are produced. You can understand how these pollutants are formed by looking at what happens to atoms during these chemical reactions.

Formulae

The chemical formula of a compound [compound: A compound is a substance formed by the chemical union (involving bond formation) of two or more elements. ] tells you how many atoms of each element the molecule contains. The table below shows the formulae of some compounds, together with the number of atoms of each element in each molecule and a diagram of each molecule.

This table shows the formulae of some compounds, with the number of atoms of each element in the molecule.

carbon monoxidecarbon dioxidesulfur dioxidenitrogen monoxidenitrogen dioxidewater (hydrogen oxide)
formulaCOCO2SO2NONO2H2O
carbon atoms11       
sulfur atoms    1     
nitrogen atoms      11  
hydrogen atoms     2
oxygen atoms122121

The small (subscript) number after a symbol tells you how many atoms of that particular element are in the molecule. If there is only one atom of an element in a molecule, we do not write the number 1 after the symbol. For example, the water molecule H2O has two hydrogen atoms and one oxygen atom.

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