Charlie is balancing an equation. She has identified the atoms and counted the number of each in the reactants and products. What would Charlie adjust to make the number of atoms in the reactants the same as the number of atoms in the products?

Charlie should adjust the coefficients—the numbers placed in front of chemical formulas—to balance the atoms. Changing coefficients changes how many molecules or formula units are present without changing what substances they are; changing subscripts would change the substances themselves.

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