Every chemical equation must obey the law of conservation of mass. In a balanced equation, the number of atoms of each element on both sides of the equation are equal. A balanced equation satisfies mass balance as well as charge balance. The chemical equation must be balanced with respect to mass because matter can neither be created nor destroyed. The equation must be balanced with respect to charge because the electrons lost by atoms to form cations are equal to the electrons gained by other atoms to form anions.
