ATOMIC THEORY Philosophical Idea to Scientific Theory

1. ATOMIC THEORY Philosophical Idea to Scientific Theory Chapter 3 Section 1

2. DEMOCRITUS 400 B.C. • A Greek philosopher • Believed that atoms were the smallest particles of matter and that different atoms comprised different materials.

3. Atom is from the Greek word atomos, meaning, indivisible. • Purely philosophical ideas at this point.

4. ARISTOTLE (300 B.C.) • Greek philosopher who rejected Democritus’ atom. • Proposed that matter was continuous. • Called contiuous matter, hyle.

5. ISAAC NEWTON and ROBERT BOYLE 1600 • Rejected Aristotle’s hyle theory in published articles. • Still did not have proof that atoms existed.

6. LAVOISIER 1700’s • The “Father of Chemistry” • One of the first scientists to use numeric data to support his hypothesis. • Proposed the Law of Conservation of Mass in 1782.

7. Law of Conservation of Mass • Matter cannot be created or destroyed during a chemical reaction. • Mass of reactants = mass of products.

8. JOSEPH PROUST late 1700’s • Observed that specific substances (compounds) always contain the same elements in the same ratio by mass. • This is known as the Law of Definite Proportions. Ex. NaCl always consists of 60.66 % chlorine and 39.43 % sodium

9. CLAUDE – LOUIS BERTHOLLET and JOHN DALTON 1790’s • Law of Multiple Proportions • When multiple compounds of the same 2 elements exist, the masses of the second element combined with a certain mass of the first is always a ratio of small whole numbers.

10. MULTIPLE PROPORTIONS • Example:

11. JOHN DALTON 1800’s • Proposed his Atomic Theory in 1808 based on the following: • Democritus’ atom • Law of conservation of mass • Law of definite proportions • Law of multiple proportions

12. All matter is composed of extremely small particles called atoms which cannot be subdivided, created or destroyed. 5 Principles of Dalton’s Atomic Theory

13. 5 Principles of Dalton’s Atomic Theory • Atoms of a given element are identical in their physical and chemical properties. • Atoms of different elements differ in their physical and chemical properties.

14. 4. Atoms of different elements combine in simple, whole number ratios to form compounds. 5 Principles of Dalton’s Atomic Theory

15. 5 Principles of Dalton’s Atomic Theory 5. In chemical reactions, atoms are combined, separated, or rearranged, but never created destroyed or changed.

16. CURRENT ATOMIC THEORY • The first principle of Dalton’s atomic theory has been refuted. • Atoms can be created and destroyed. • Atoms can be subdivided into subatomic particles: • Proton • Neutron • Electron • How were each of these discovered?

17. INTERNET RESEARCH • Use the internet to complete the next few pages of your note guide. Name the experiment, read the procedures and determine the major conclusions of each.

18. SCIENTISTS of INTEREST: JJ Thomson, Robert Millikan, and Earnest Rutherford EXPERIMENTS: Cathode Ray Tube, Oil Drop, and the Gold Foil Experiment.

19. ADDITIONAL SUBATOMIC PARTICLES • Who discovered the neutron? • What is a quark? Find the names and characteristics of the quarks.