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FRESHMAN CHEMISTRY 124, Handout 2: Chapter 2
DALTON'S ATOMIC THEORY EXPLAINS THE LAW OF CONSTANT COMPOSITION
1. MATTER is composed of small, indivisible particles called atoms. 2. The atoms of a given element all have the same mass and are identical in all respects, including chemical behavior. 3. Chemical compounds are composed of two or more different atoms joined together. The particle that results when two or more atoms join together is called a molecule. The atoms in a molecule do not necessarily have to be different. If the atoms are the same, it is a molecule of an element. If the atoms are different, it is a molecule of a compound. 4. COMPOUNDS are formed by the combination of different atoms in the ratio of small whole numbers. NH3, HCl, Cl2, CH4. 5. LAW OF CONSTANT COMPOSITION: the relative amount of each element in a particular compound is always the same, regardless of the source of the compound or how the compound is prepared. 6. A CHEMICAL REACTION involves only the combination, separation, or rearrangement of atoms; atoms are neither created nor destroyed in the course of ordinary chemicals. 7. LAW OF CONVERSATION OF MASS: in a chemical reaction, the total mass of the reacting substances is equal to the total mass of the products formed. 8. LAW OF MULTIPLE PROPORTIONS: atoms combine in the ratio of small whole numbers. H2O, H2O2
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