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Topic 7: Atomic and Nuclear Physics

Topic 7: Atomic and Nuclear Physics. A brief history of nuclear physics:. We will be creating a timeline as a class. Each group will be given a specific year or event. Using a computer, your task, as a group:

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Topic 7: Atomic and Nuclear Physics

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  1. Topic 7: Atomic and Nuclear Physics

  2. A brief history of nuclear physics: • We will be creating a timeline as a class. • Each group will be given a specific year or event. Using a computer, your task, as a group: • Determine what significant event in/related to nuclear physics occurred in that year (or which year the event occurred) • Determine which scientist(s) were involved • Be prepared to present a BRIEF summary of the event (you are not expected to understand/have details…those will come later!) • You will have 15 minutes max to complete this task! • Following your brief presentation, you will fill in the class timeline with your information

  3. Atomic Structure…a brief timeline: • Two distinct models of the structure of an atom: • 1897-1904: JJ Thomson • 1909-11: Ernest Rutherford • Use the resources provided to create a detailed, labeled set of illustrations to compare these two models of atomic structure • 1 Poster per group • Diagrams, labels, and caption describing the model are all required. Due in 20 minutes.

  4. J.J. Thomson: “Plum Pudding” model • An atom is a mixture of positive and negative charges Image from: http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec11.html

  5. 1909-1911: Rutherford’s work… Gold-Foil Experiment: • Very thin gold foil • Focused a beam of Helium nuclei • Observed the result of colliding the He nuclei with the Gold foil http://bhs.smuhsd.org/science-dept/marcan/apchemistry/structure_ML_MD.html

  6. Gold Foil Experiment: Rutherford, Geiger, and Marsden • Expected Results: • Positive Helium Nucleus would pass straight through the gold foil or only be slightly deflected… • Actual Results: • Most particles DID pass straight through with little to no deflection… • However: Several had unexpectedly large deflection angles!

  7. Ernest Rutherford—several years after the Gold Foil Experiment "It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you."

  8. Rutherford’s Conclusion: • Atoms have a dense, positively charged center (later called the nucleus) and the electrons must be in the space surrounding the nucleus • Completely different model than Thomson’s “Plum Pudding” model

  9. Rutherford’s Conclusion: Image from: http://abyss.uoregon.edu/~js/ast123/lectures/lec04.html

  10. Planetary Model • Massive, positively charged nucleus • Electrons orbited much like planets around the Sun • The Coulombic (electrostatic) force of attraction between the positive protons and the negative electrons kept the electrons in orbit

  11. Makes sense…what’s the problem?

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