Write down the chemical formulas of all substances involved in the the reaction, separating them with an arrow. The arrow represents transformation from one state to another. For example, the reaction of aluminum and oxygen to form aluminum oxide would be written as Al + O2 --> Al2O3.
Compare the number of atoms of each element on both sides of the equation, denoted by a subscript.
Starting with the largest compounds' elements, add whole number coefficients to both to ensure both compounds have the same number of atoms of each element. Multiply the coefficient by each subscript to get the number of atoms. Using the aluminum oxide example, Al +O2 --> Al2O3 does not balance.
Aluminum balances with a coefficient of 2 on the left side of the equation to match the aluminum atoms on the right, but oxygen requires a different approach--3 divided by 2 is 1.5, which would represent 1.5 molecules, an impossible amount. To eliminate the half, add coefficients of 2 to both sides: 2(2Al + 1.5O2)--> 2(Al2O3). This leaves 4Al+3O2-->2Al2O3.
Avoid balancing hydrogen and oxygen first--according to Pennsylvania State University--because these elements appear in many compounds. Instead, focus on the other elements. Balance polyatomic ions as whole units if they remain intact throughout the reaction.
Using iron (III) sulfate as an example, Fe3+ + (SO4)2-, the iron has a positive charge of 3, whereas the sulfate has a negative charge of 2. (Fe3+)2(SO4(2-))3 increases the charge on both sides to 6, resulting in a net zero charge.
Draw a table and count up all elements on both sides of the equation. All measurements should be equal.