AP Chemistry A. Allan Chapter 2 Notes - Atoms, Molecules and Ions 2.1 The Early History Refer to the Chemistry History Timeline for this chapter 2.2 Fundamental Chemical Laws A. Law of Conservation of Mass 1. "Mass is neither created nor destroyed" 2. Translation: In ordinary chemical reactions, the total mass of the reactants is equal to the total mass of the products B. Law of Definite Proportion 1. "A given compound always contains the same proportions of elements by mass" 2. Translation: Compounds have an unchanging chemical formula C. Law of Multiple Proportions 1. "When two elements form a series of compounds, the ratios of the masses of the second element that combine with one gram of the first element can always be reduced to small whole numbers