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1803

1803. Key words. John Dalton Father of the Modern Atomic Theory. Postulate #1. Experiment/postulates Know all 5!!!. Elements are composed of atoms, which are very small, indivisible, indestructible particles. True or Wrong?. Wrong. ……we know about subatomic particles. Postulate #2.

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1803

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  1. 1803 Key words • John Dalton • Father of the Modern Atomic Theory

  2. Postulate #1 Experiment/postulates Know all 5!!! • Elements are composed of atoms, which are very small, indivisible, indestructible particles. • True or Wrong?

  3. Wrong ……we know about subatomic particles.

  4. Postulate #2 • All atoms are of the same element are identical. • True or Wrong??

  5. Wrong ….they aren’t exactly the same because of isotopes (atoms with same number of protons but different number of neutrons).

  6. Postulate #3 • Atoms of different elements have different properties. • True or Wrong??

  7. Postulate #4 • Atoms combine in small, whole-number ratios to form compounds. • True or Wrong?? Two Hydrogen One Oxygen H2O

  8. Postulate #5 • Atoms of one element cannot change into an atom of a different element during a chemical reaction. • True or Wrong??

  9. 1897 Experiment Key words JJ Thompson Electrons discovered by experiments with cathode ray tubes + magnetic field - Magnetic field Electron stream w/o applied magnetic field Electron stream after applied magnetic field **He was finally able to show that the beam could be deflected by an electric field, and thus consisted of NEGATIVELY CHARGED PARTICLES (AKA ELECTRONS) discovery sketch

  10. 1904 • JJ Thompson again… • Published atomic theory that’s now known as Plum Pudding Model • Thought electrons moved randomly in a positively charged, amorphous “pudding” or cloud Another Experiment Actual plum pudding!

  11. 1909 Key words • Rutherford • Gold Foil Experiment • nucleus

  12. 1911 Experiment • Rutherfords discovery: 1.The atom has a dense, positively charged core (aka nucleus) which contains most of the mass. 2.Most of the atom is empty space. The electrons are somehow moving around the empty space. Discovery sketch

  13. 1915 Important words Discovery Negative electron • Niels Bohr proposes the Bohr Model, also called the Planetary model • This states the electrons orbit the nucleus much like planets around the sun (which we now know is not exactly how electrons travel!) Nucleus (positively charged) sketch

  14. What we know now! Watch this video… http://www.youtube.com/watch?v=K-jNgq16jEY Now we know that electrons travel around the nucleus, not in circles but in different shaped patterns!

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