Chapter 2 Atoms
Atoms • Greek philosopher, Democritus fifth century B.C., coined term atom, as particles that can not be cut or broken up further.
Law of Conservation of Mass • Antoine Lavosier- found when a reaction occurred in a closed system, total mass of system remained unchanged.
Law of Conservation of Mass • Matter is neither created nor destroyed during chemical changes. Thus the total mass of the reactants must equal the mass of the products.
Law of Definite Proportions • Many compounds are made of more than one element • Each element has the same proportion in a compound, regardless of where it was made
Joseph Proust • Copper carbonate from various sources always had same composition • Always 36.18% oxygen, 57.48% copper, 5.43% carbon and 0.91% hydrogen
Law of Definite Proportions • A compound always contains the same elements in certain definite proportions and no other combinations.
Atomic Theory of Matter • John Dalton-1803- explain data • 1) All matter made of extremely small particles called atoms • All atoms of a given element are alike, but atoms of different atoms are different. • Compounds are formed when atoms of different elements combine in fixed proportions.
4. A chemical reaction involves rearrangement of atoms. No atoms are created or destroyed.
Modern Modifications • Atoms not completely indivisible • Not all atoms of an element are completely alike • Number of atoms in a molecule usually a simpler ratio
Example • Jons Berzelius found • 10g lead + 1.55g sulfur --- 11.55g Pbsulfate