In every balanced chemical equation, each side of the equation has the same number of <u>atoms</u> of reactants and products.
For example, let's take this chemical equation.
This is the chemical equation for carbon monoxide reacting with dihydrogen to form octane and water.
8 CO + 17 H2 → C8H18 + 8 H2O
On this side, we have 8 carbon monoxide atoms and 34 dihydrogen atoms.
On the other side, we have 8 carbon atoms and 18 hydrogen atoms + 16 hydrogen atoms.
Therefore, even though the coefficients are different there is still an equal number of atoms on each side.
8 Carbon Monoxide , 34 Dihydrogen = 8 Carbon Monoxide + 34 Dihydrogen