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Atomic Theorists

Atomic Theorists

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Atomic Theorists

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  1. Atomic Theorists A Photographic Chronology by David Snyder Seton Hall Prep School

  2. Let’s start in Ancient Greece around 400 B.C. Home of Democritus

  3. Democritus - the happy philosopher ATOMOS!!!

  4. Move to England - 1804 Model John Dalton Elements always combine in whole number ratios. That means atoms never break apart. They are INDIVISIBLE!

  5. Let’s stay in England and meet Sir Joseph John Thomson. Busy with his Cathode Ray Tube Experiment. (1897)

  6. A closer look at the CRT. High voltage causes a gas to produce a beam of light.

  7. The atoms in the tube are neutral. • They have no positive or negative charge - they have no charge at all. • An atom walks into a bar, gets a drink, then says to the bartender, “What do I owe ya?” The bartender says...

  8. FOR YOU... NO CHARGE!

  9. Even though atoms have no charge, JJ noticed something odd. negative magnet

  10. The light bent toward the + magnet and away from the - one. What charge were the particles in the light?

  11. BUT ATOMS HAVE NO CHARGE • The particles bent to the positive magnet. • The particles must be NEGATIVE. • Atoms have no charge so these particles are PART of the atom. • The atom is NOT indivisible!!!

  12. The negatives are spread through the atom like... plums in plum pudding.

  13. Marie Curie (and Pierre) • In 1898 discovered that samples of uranium released energy. • The energy was proportional to the amt. of uranium. • No manipulations could alter the E. • The E must have been released FROM the atoms

  14. Now on to JJ’s friend - Ernest Rutherford. 1909

  15. Continued work with radiation.

  16. Rutherford’s Gold Foil Experiment

  17. Rutherford EXPECTED the + particles to cruise through the foil Microscale view Macroscale view

  18. But that is not what he witnessed! The + particles hit all over. Why?

  19. Rutherford’s Summary • Most of the + went straight through. • Some deflected off to the sides. • These must have hit a like + charge that was very small and dense. • The rest of the atom is - space.

  20. So the atom must look like this...

  21. Be careful Ernie. The - electrons are attracted to the + nucleus so... The atom would collapse on itself and we know that doesn’t happen.

  22. His buddy, Niels Bohr believed that negatives (electrons) were held in orbits.

  23. Today, we accept a modified model of the Bohr model. Check some BASICS at these pages: http://www.quia.com/mc/239926.html http://www.pbs.org/wgbh/aso/tryit/atom/

  24. The end... Of this presentation but not for atomic research