Developing an Atomic Theory

1. Developing an Atomic Theory • Part 2 The Quantum Experience

2. Review • Democritus developed the first atomic theory.

3. Review • Democritus developed the first atomic theory. • around 400 B.C.

4. Review • Democritus developed the first atomic theory. • around 400 B.C. • descriptive not functional

5. Review • Democritus (400 B.C.)

6. Review • Democritus (400 B.C.) • Dalton developed the first modern atomic theory.

7. Review • Democritus (400 B.C.) • Dalton developed the first modern atomic theory. • published in 1803

8. Review • Democritus (400 B.C.) • Dalton developed the first modern atomic theory. • published in 1803 • based on observations of himself and others

9. Review • Democritus (400 B.C.) • Dalton developed the first modern atomic theory. • published in 1803 • based on observations of himself and others • still descriptive and not functional

10. Review • Democritus (400 B.C.) • Dalton (1803)

11. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson discovered the electron.

12. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson discovered the electron. • using the cathode ray tube in 1897

13. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson discovered the electron. • using the cathode ray tube in 1897 • developed the plum pudding model

14. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson (1897)

15. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson (1897) • Nagaoka proposed a model with a central nucleus for an atom.

16. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson (1897) • Nagaoka proposed a model with a central nucleus for an atom. • proposed in 1904

17. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson (1897) • Nagaoka proposed a model with a central nucleus for an atom. • proposed in 1904 • not well publicized in Europe and America

18. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson (1897) • Nagaoka (1904)

19. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson (1897) • Nagaoka (1904) • Rutherford discovered the nucleus.

20. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson (1897) • Nagaoka (1904) • Rutherford discovered the nucleus. • Developed the solar system model in 1911

21. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson (1897) • Nagaoka (1904) • Rutherford (1911)

22. Review • Democritus (400 B.C.) • Dalton (1803) • J. J. Thomson (1897) • Nagaoka (1904) • Rutherford (1911) • That is where we left off.

23. Problem • There is a problem with the solar system model.

24. Problem • There is a problem with the solar system model. • Classical physics says that as a charged particle moves in a circle, it emits energy.

25. Problem • There is a problem with the solar system model. • Classical physics says that as a charged particle moves in a circle, it emits energy. • As the electron emits energy, its orbital energy should decay.

26. Problem • There is a problem with the solar system model. • Classical physics says that as a charged particle moves in a circle, it emits energy. • As the electron emits energy, its orbital energy should decay. • The electron should spiral into the nucleus.

27. Problem • There is a problem with the solar system model. • Classical physics says that as a charged particle moves in a circle, it emits energy. • As the electron emits energy, its orbital energy should decay. • The electron should spiral into the nucleus.

28. Problem • There is a problem with the solar system model. • Classical physics says that as a charged particle moves in a circle, it emits energy. • As the electron emits energy, its orbital energy should decay. • The electron should spiral into the nucleus. • It should take about 1/1,000,000,000 of a second.

29. Problem • There is a problem with the solar system model. • Classical physics says that as a charged particle moves in a circle, it emits energy. • As the electron emits energy, its orbital energy should decay. • The electron should spiral into the nucleus. • It should take about 1/1,000,000,000 of a second. • But, electrons don’t spiral into the nucleus!

30. Problem • There is a problem with the solar system model. • We need a newer, more realistic model of the atom.

31. Problem • There is a problem with the solar system model. • We need a newer, more realistic model of the atom. • Here comes the quantum model.

32. Max Planck

33. Max Planck • Max Planck said that energy is in packets he called “quanta.”

34. Max Planck • Max Planck said that energy is in packets he called “quanta.” • That is, the energy in a system increases or decreases in steps.

35. Max Planck • Max Planck said that energy is in packets he called “quanta.” • That is, the energy in a system increases or decreases in steps. • This is contrary to what is predicted by classical physics.

36. Max Planck • Max Planck said that energy is in packets he called “quanta.” • That is, the energy in a system increases or decreases in steps. • This is contrary to what is predicted by classical physics. • Today, we call those energy packets photons.

37. Max Planck • The energy in a photon depends on the frequency of the light.

38. Max Planck • The energy in a photon depends on the frequency of the light. • Energy, E, is equal to a constant, h, (Planck’s constant), times the frequency of the light, ν (lower case Greek letter nu).

39. Max Planck • The energy in a photon depends on the frequency of the light. • Energy, E, is equal to a constant, h, (Planck’s constant), times the frequency of the light, ν (lower case Greek letter nu). • E = hν

40. Max Planck • The energy in a photon depends on the frequency of the light. • Energy, E, is equal to a constant, h, (Planck’s constant), times the frequency of the light, ν (lower case Greek letter nu). • E = hν • Presented in 1900.

41. Albert Einstein

42. Albert Einstein • Albert Einstein made use of these quanta to explain the photoelectric effect.

43. Albert Einstein • The photoelectric effect:

44. Albert Einstein • The photoelectric effect: • If we shine blue light on the surface of a piece of metal, electrons are ejected from the metal.

45. Albert Einstein • The photoelectric effect: • If we shine blue light on the surface of a piece of metal, electrons are ejected from the metal.

46. Albert Einstein • The photoelectric effect: • If we shine red light on the surface of a piece of metal, no electrons are ejected from the metal.

47. Albert Einstein • The photoelectric effect: • If we shine red light on the surface of a piece of metal, no electrons are ejected from the metal.

48. Albert Einstein • In 1905, Einstein published four papers that contributed substantially to the foundations of modern physics.

49. Albert Einstein • In 1905, Einstein published four papers that contributed substantially to the foundations of modern physics. • The first one published focused on the photoelectric effect.

50. Albert Einstein • Einstein said that we needed to look at light as a particle, not as a wave.