A chemical equation shows what happens in a chemical reaction. As in any equation, the elements on the left side of the equation (the reactants) must equal the elements on the right (the products). Here are just a few things to remember when balancing chemical equations:

**Same elements in equal numbers:**For an equation to be balanced, it must have the same number of*each*element on each side of the equation. The mass of the reactants has to equal the mass of the products — remember the law of conservation of mass?**Same charge:**If there’s a net charge on one side of the equation, the other side of the equation must have the same charge.**Unchanged chemical formulas:**Most importantly, never alter a chemical formula! Subscripts (and superscripts for that matter) do not magically change. Change only the coefficients.