Catalyst

1. Catalyst 1. What are the two subatomic particles found in the nucleus? 2. What is the mass of protons, neutrons, and electrons? 3. How many cuts were you able to make during your aluminum atom lab?

2. It takes 31 cuts to get to the size of the atom! It is 0.0000007 mm!

5. Mercury Poisoning Reading • Complete the reading with a partner • You must answer all questions individually

6. Development of Atomic Theory

7. Today’s Learning Targets I can explain the development of atomic theory incorporating the contributions of Dalton, Thomson, Rutherford, and Bohr.

8. What was Dalton’s contribution to atomic theory?

9. I. Dalton’s Model of the Atom Draw this!

10. What was Thomson’s contribution to atomic theory?

11. I. J. J. Thomson • First evidence for subatomic particles. • Made discovery in 1896.

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13. II. J. J. Thomson’s Experiment • Cathode-ray tube

14. II. J.J. Thomson’s Experiment • Put a battery to the cathode tube and saw a beam form. • The beam contained subatomic particles. • Positive magnet next to beam = bent towards magnet. • Negative magnet next to beam = bent away from magnet.

15. III. Thomson’s Discovery • Thomson discovered the electron! • He discovered that atoms must contain some negatively charged particlescalled electrons. • Tells us nothing about the location of the electron.

16. IV. Plum Pudding Model • Thompson proposed that electrons were balls of negative charge floating in a sea of positive charges. Draw this!

17. What was Rutherford’s contribution to atomic theory?

18. I. Ernest Rutherford • Disproved Plum Pudding Model with Gold Foil Experiment • Used alpha particles, which are small, positively charged particles.

19. II. Rutherford’s Experiment • Shot positively charged alpha particles at gold foil • Most particles went through foil. • Small amount of the particles were deflected • Smaller amount were bounced back

21. Justify – TPS • Using Rutherford’s data below, make a hypothesis about what this data indicates.

22. Rutherford noted: “It was almost as if you fired a 15-inch shell into a piece of tissue paper and it came back and hit you.”

24. III. What Rutherford’s Data Meant • Most alpha particles went straight through = atom is mostly empty space. • Some alpha particles deflected = they came close to other electrons. • Small amount bounced back = hitting a very small, but very dense positively charged nucleus.

27. IV. Important Point #1 • The atom is mostly empty space.

28. V. Important Point #2 • The atom has very small, but very densenucleus. • Alpha particles that bounced back were coming into contact with nucleus.

29. What was Bohr’s contribution to atomic theory?

30. I. NielsBohr • Refined Rutherford’s model of the atom.

33. II. What Bohr Knew • Shooting electricity through the hydrogen excites electrons. • Color produced only 4 specific values • Problem – If electrons were free to roam, then we should get all sorts of colors

34. III. Bohr’s Solution • Electrons are not free to roam in the electron cloud, electrons are restricted to orbits

36. The Modern Model Dalton’s atom Thompson’s electrons Rutherford’s space and nucleus Bohr’s energy levels

37. Exit Ticket

38. Homework Due Friday: Read Ch. 4 and complete odd numbered questions at end of each section (Questions 4.1-4.43)