1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The activity 1.Break into your groups and move the desks out of the way so that you can work on the floor. 2.Organize the cards from lowest to highest mass. 3.Next, look for elements with similar properties. 4.Organize the cards with similar properties in the same group. 5.Pay attention to chloride and oxide formations. 6.Ask for help if you need it.

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Objectives TLW explain the earth, fire, wind, water model of the atom TLW state the five essential aspects of Dalton’s atomic theory TLW compare and contrast the Greek model and Dalton’s model TLW explain the law of conservation of mass Chapter 4

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Objective (that has nothing to do with science) Explain the ancient origins of atomic theory. Chapter 4

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Introduction Atomic theory first originated with Greek philosophers around 2500 years ago. This basic theory remained unchanged until the 19 th century when it first became possible to test the theory with more sophisticated experiments.

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Ancient Atomic Theory The atomic theory of matter was first proposed by Leucippus, a Greek philosopher who lived around 400BC. At this time the Greeks were trying to understand matter. According to Leucippus, if one attempted to divide matter forever, eventually you arrive at small particles which can not be further subdivided. We now call these indivisible particles atoms (from the Greek word atomos, meaning “indivisible”). Leucippus Introduction

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Ancient Atomic Theory Leucippus's atomic theory was further developed by his disciple, Democritus who concluded that infinite divisibility of a substance belongs only in the imaginary world of mathematics. Democritus Introduction

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Ancient Atomic Theory According to the ancient Greeks, atoms were all made of the same basic material, but atoms of different elements had different sizes and shapes. The sizes, shapes, and arrangements of a material’s atoms determined the material’s properties. It was believed that there were four elements that all thing were mare from; Earth, Air, Fire and Water. Introduction

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The law of multiple proportions This law states that when elements combine they do so in a ratio of small whole numbers. For example, carbon and oxygen react to form CO or CO 2, but not CO 1.3. The English chemist John Dalton first expressed this observation in 1803. Chapter 3

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Dalton’s Atomic Theory 1) All matter is composed of extremely small particles called atoms. 2) Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties. 3) Atoms cannot be subdivided, created, or destroyed. Chapter 3

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Dalton’s Atomic Theory, continued 4) Atoms of different elements combine in simple whole-number ratios to form chemical compounds. 5) In chemical reactions, atoms are combined, separated, or rearranged. Chapter 3

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Modern Atomic Theory Not all aspects of Dalton’s atomic theory have proven to be correct. We now know that: Chapter 3 Some important concepts remain unchanged. Atoms are divisible into even smaller particles. A given element can have atoms with different masses. All matter is composed of atoms. Atoms of any one element differ in properties from atoms of another element.