It is important to balance chemical equations because there must be an equal number of atoms on both sides of the equation to follow the Law of the Conservation of Mass. This chemical law states that in order for the equation to be correct, "An equal quantity of matter exists both before and after the experiment; the quality and quantity of the elements remain precisely the same."
The Law of Conservation of Mass was discovered by Antoine Laurent Lavoisier in 1789. He discovered that matter cannot either be created or destroyed. The number on either side of the equation must be exactly the same when the equation is finished as it was when it began.
Equations that are not properly balanced are not correct chemical equations, even if they posses the correct elements and quantities. Unbalanced equations are known as skeletal equations and cannot be used in calculating chemical reactions. Creating a balanced equation rather than using a skeletal equation is very important, as the number of atoms in a chemical compound always remains the same. Atoms cannot be added to or disappear from an equation. By making sure the chemical equation is properly balanced, the mass of the chemical compound is correctly preserved.