Which of the following statements is/are true? A. A balanced chemical equation has an equal number of atoms of all elements in the reactants and products. B. An unbalanced chemical equation has an unequal number of atoms of one or more elements in the reactants and products.

Statement A is true; a balanced chemical equation ensures that the number of atoms of each element is the same on both sides of the equation, conserving mass. Statement B is also true; an unbalanced chemical equation indicates that there is an unequal number of atoms of one or more elements in the reactants and products, which does not comply with the law of conservation of mass.