Why is learning about the atom important….? <ul><li>The atom was considered to be an “imaginary” thing, something that peo...
In Hiroshima, of a resident civilian population of 250 000 it was estimated that 45 000 died on the first day and a furthe...
Early Atomic Ideas <ul><li>Democritus  (5th c. BC):  matter was made up of things that were indestructible,  unchanging & ...
Dalton’s Atomic Theory <ul><li>TOOK WORK OF PREVIOUS SCIENTISTS & ASSEMBLED IT: (5 postulates) </li></ul><ul><li>All matte...
The Early 1800’s! <ul><li>Lots of introductory work with electricity </li></ul><ul><li>Matter is electrical in nature! </l...
But technology was limited until the late 1800’s, early 1900’s…. <ul><li>With technology comes experimentation! </li></ul>...
Cathode Ray Tube, or Crooke’s Tube <ul><li>Evacuated tube containing two metal electrodes or plates connected to a battery...
So what are Cathode Rays….? <ul><li>J.J. Thomson, in 1897, answered this question! </li></ul><ul><li>Two charged plates we...
The cathode ray tube was the precursor to the modern day….. TELEVISION! Black and White….. Color…….
Millikan Oil-Drop Experiment <ul><li>Robert Millikan in 1909 discovered the charge and mass of an electron </li></ul><ul><...
Now that we have found negative particles…. <ul><li>Eugen Goldstein in late 1800’s  used a Crooke’s tube with holes in the...
<ul><li>The electrons from the atoms went with the beam of electrons to the + plate </li></ul><ul><li>He also observed + p...
Who puts all of this information together into “The Big Picture”? <ul><li>J.J. Thomson theorized that these negative and p...
Why was any of this monumental…? <ul><li>People didn’t believe in atoms, and didn’t understand what things like electricit...
So atoms are made of + and - particles.  How are some atoms “radioactive”?  What is “radioactivity”?  <ul><li>Henri Becque...
Ernest Rutherford was determined to figure out what this “radiation” was!  <ul><li>Ernest Rutherford, a physicist from New...
Rutherford’s Radiation Experiment
In Summary,  No mass, but speed of light! Can be dangerous! 0 0 Gamma   Fast, but no mass so little energy -1 0 Beta ( ...
<ul><li>Atoms, we know, contain protons, neutrons, and electrons </li></ul><ul><li>Up until this point, only protons and e...
The Gold Foil Experiment…. What is happening?  Why are the alpha particles bouncing off?
Gold Foil Experiment Rutherford's Experiment
What is going on….? <ul><li>The alpha particles are bouncing off of something! </li></ul><ul><li>What charge does an alpha...
Why did he think that ALL the protons were in the center? <ul><li>Alpha particles are huge! </li></ul><ul><li>They contain...
Rutherford’s “nuclear” model!
What is the relative size of the atom….? <ul><li>An atomic model the size of Busch Stadium and parking would contain a pea...
So why do some atoms give off radiation???? <ul><li>Rutherford looked at his model of the atom for answers! </li></ul><ul>...
……..The neutron does! <ul><li>The neutron was the last particle to be discovered! </li></ul><ul><li>Why was it the last pa...
Problems after element 82….. <ul><li>After lead, element 82,  there are too many protons in the nucleus, and no number of ...
In summary….. <ul><li>We know that the nucleus contains… </li></ul><ul><li>Protons and neutrons! </li></ul><ul><li>And the...
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Atomic Experiments Regular Fall07

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History of atomic theory through Rutherford's model of the atom.

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  • Thanks for this slide show, it was interesting to understand, I knew some, but it was very refreshing and more indepth than just saying 'there is a nucleus with electrons spinning around it'. Plus for further mysteries to be solved, we need to understand the basics, its one link after another till the bridge is crossed.
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  • you should make more amount of slide.
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Atomic Experiments Regular Fall07

  1. 1. Why is learning about the atom important….? <ul><li>The atom was considered to be an “imaginary” thing, something that people laughed at! </li></ul><ul><li>Roosevelt trusted Einstein, and funded his secret research known as the “Manhattan Project” </li></ul><ul><li>In a few short years, the idea of an invisible atom had been developed into a city-destroying weapon - the atomic bomb! </li></ul>
  2. 2. In Hiroshima, of a resident civilian population of 250 000 it was estimated that 45 000 died on the first day and a further 19 000 during the subsequent four months. In Nagasaki, out of a population of 174 000, 22 000 died on the first day and another 17 000 within four months. Over 90% of each city was destroyed.
  3. 3. Early Atomic Ideas <ul><li>Democritus (5th c. BC): matter was made up of things that were indestructible, unchanging & different </li></ul><ul><li>atomos = indivisible </li></ul><ul><li>Aristotle: Didn’t believe in atoms! </li></ul>
  4. 4. Dalton’s Atomic Theory <ul><li>TOOK WORK OF PREVIOUS SCIENTISTS & ASSEMBLED IT: (5 postulates) </li></ul><ul><li>All matter is made up of atoms </li></ul><ul><li>Atoms are indivisible (Democritus) </li></ul><ul><li>Atoms cannot be created or destroyed, just rearranged (Lavoisier) </li></ul><ul><li>Atoms combine in whole number ratios to form compounds (Proust) </li></ul><ul><li>Atoms of one element are identical to each other, but different than atoms of differing atoms </li></ul>
  5. 5. The Early 1800’s! <ul><li>Lots of introductory work with electricity </li></ul><ul><li>Matter is electrical in nature! </li></ul><ul><li>Ben Franklin assigns + & - charges to charged objects (didn’t know it had to do with the atom!) </li></ul>
  6. 6. But technology was limited until the late 1800’s, early 1900’s…. <ul><li>With technology comes experimentation! </li></ul><ul><li>With these experiments, what part of the atom do you think was the first to be discovered…..? </li></ul>………… ..THE ELECTRON! Why do you think it was the first to be discovered……?
  7. 7. Cathode Ray Tube, or Crooke’s Tube <ul><li>Evacuated tube containing two metal electrodes or plates connected to a battery </li></ul><ul><li>William Crookes designed this tube in 1879 </li></ul><ul><li>The cathode ray inside glows green </li></ul><ul><li>Crookes was convinced this beam consisted of charged particles </li></ul>
  8. 8. So what are Cathode Rays….? <ul><li>J.J. Thomson, in 1897, answered this question! </li></ul><ul><li>Two charged plates were used above and below the beam </li></ul><ul><li>The Beam was attracted to + plate, and was deflected from – plate! </li></ul><ul><li>CRT Demo </li></ul><ul><li>Conclusion: cathode rays were composed of negatively charged particles called electrons! </li></ul>
  9. 9. The cathode ray tube was the precursor to the modern day….. TELEVISION! Black and White….. Color…….
  10. 10. Millikan Oil-Drop Experiment <ul><li>Robert Millikan in 1909 discovered the charge and mass of an electron </li></ul><ul><li>He placed electrically charged oil drops in an electric field </li></ul><ul><li>The oil drops were sprayed into the upper chamber </li></ul><ul><li>Some drops gained – charge (static electricity) & were repelled by the - plate </li></ul><ul><li>Millikan Oil Drop Demo </li></ul>
  11. 11. Now that we have found negative particles…. <ul><li>Eugen Goldstein in late 1800’s used a Crooke’s tube with holes in the cathode and discovered positive particles </li></ul><ul><li>He shot a cathode beam (beam of electrons) at hydrogen atoms </li></ul>
  12. 12. <ul><li>The electrons from the atoms went with the beam of electrons to the + plate </li></ul><ul><li>He also observed + particles moving backwards towards the + plate and going through the holes! </li></ul><ul><li>Different amounts of + particles were produced when different gases were used because each element has a different number of protons! </li></ul><ul><li>Canal Rays Demo </li></ul>
  13. 13. Who puts all of this information together into “The Big Picture”? <ul><li>J.J. Thomson theorized that these negative and positive particles were actually part of matter - part of the atom! </li></ul><ul><li>He develops the first working model of the atom, known as the plum pudding model! </li></ul><ul><li>Dalton’s idea that atoms were solid particles like marbles that weren’t made of smaller pieces was…REJECTED! </li></ul>
  14. 14. Why was any of this monumental…? <ul><li>People didn’t believe in atoms, and didn’t understand what things like electricity and light were! </li></ul><ul><li>Thomson showed that electricity was nothing more than a flow of little particles called electrons! </li></ul><ul><li>And electrons, along with protons, make up every atom, in every person, plant, building and object in the universe </li></ul><ul><li>We are made of charged particles - the same particles that we use for electricity </li></ul>
  15. 15. So atoms are made of + and - particles. How are some atoms “radioactive”? What is “radioactivity”? <ul><li>Henri Becquerel , in 1895, put a chunk of Uranium in a desk drawer with some photographic paper </li></ul><ul><li>Becquerel knew the Uranium atoms must be giving “something” off. He called this something “radioactivity” or “ radiation ”. </li></ul><ul><li>The same year, William Roentgen had a similar experience - his Uranium actually caused photographic paper to develop in a nearby lab - through a wall! </li></ul><ul><li>He called his rays, “ X-Rays ”. They were immediately used for medical purposes! </li></ul><ul><li>What was this “radiation”, though? How did it relate to what Thomson had discovered? </li></ul>
  16. 16. Ernest Rutherford was determined to figure out what this “radiation” was! <ul><li>Ernest Rutherford, a physicist from New Zealand, took a chunk of uranium, and set out to determine what it “gave off”! </li></ul><ul><li>He placed the Uranium in a lead box </li></ul><ul><li>He took two charged plates, and placed them above and below the beam of “radiation” that the Uranium was giving off </li></ul><ul><li>It split into three beams!!! </li></ul><ul><li>Radiation scattering demo </li></ul>
  17. 17. Rutherford’s Radiation Experiment
  18. 18. In Summary, No mass, but speed of light! Can be dangerous! 0 0 Gamma  Fast, but no mass so little energy -1 0 Beta (  Slow and no energy +2 4 Alpha (  Speed and Energy charge Mass (amu) Type of radiation
  19. 19. <ul><li>Atoms, we know, contain protons, neutrons, and electrons </li></ul><ul><li>Up until this point, only protons and electrons were known! </li></ul><ul><li>Why did some atoms give off radiation? </li></ul><ul><li>To answer this question, we have to look back at the structure of the atom! </li></ul>Why do atoms give off radiation, then? <ul><li>People still accepted Thomson’s model of the atom! </li></ul><ul><li>His model was wrong though! </li></ul>
  20. 20. The Gold Foil Experiment…. What is happening? Why are the alpha particles bouncing off?
  21. 21. Gold Foil Experiment Rutherford's Experiment
  22. 22. What is going on….? <ul><li>The alpha particles are bouncing off of something! </li></ul><ul><li>What charge does an alpha particle have? </li></ul><ul><li>What could it be bouncing off of? </li></ul><ul><li>They must be bouncing off of something that is…. </li></ul><ul><li>Positive! </li></ul><ul><li>And big! </li></ul><ul><li>Rutherford theorized that all of the protons weren’t scattered about, but were all concentrated into a dense center, which he called the nucleus! </li></ul><ul><li>The electrons must be orbiting around this nucleus! Why????? </li></ul>
  23. 23. Why did he think that ALL the protons were in the center? <ul><li>Alpha particles are huge! </li></ul><ul><li>They contain 2 protons and 2 neutrons! </li></ul><ul><li>They have a positive charge, because neutrons have no charge! </li></ul><ul><li>Like charges…. </li></ul><ul><li>REPEL </li></ul><ul><li>But one proton wouldn’t have enough force to push away an alpha particle coming in! </li></ul><ul><li>He knew that there must be MANY protons in the center blocking the alpha particles! </li></ul>
  24. 24. Rutherford’s “nuclear” model!
  25. 25. What is the relative size of the atom….? <ul><li>An atomic model the size of Busch Stadium and parking would contain a pea sized nucleus containing 95.95% of the atoms mass. </li></ul><ul><li>The pea at the pitcher’s mound would be the nucleus, and an ant crawling on the parking lot outside would be an electron! </li></ul><ul><li>The atom is mostly….. </li></ul><ul><li>Empty space! Nothing! </li></ul>
  26. 26. So why do some atoms give off radiation???? <ul><li>Rutherford looked at his model of the atom for answers! </li></ul><ul><li>All of the protons are jammed into a tiny little nucleus! </li></ul><ul><li>And they all have what charge….? </li></ul><ul><li>The same charge! Positive! </li></ul><ul><li>Which means….. </li></ul><ul><li>They are constantly trying to push each other out! Like charges REPEL! </li></ul><ul><li>What keeps them in there…..? </li></ul>
  27. 27. ……..The neutron does! <ul><li>The neutron was the last particle to be discovered! </li></ul><ul><li>Why was it the last particle to be discovered….? </li></ul><ul><li>IT HAS NO CHARGE! </li></ul><ul><li>It was discovered when James Chadwick noticed that Beryllium atoms were giving off some “unknown particle” when hit with alpha radiation! </li></ul><ul><li>These particles were neutrons! </li></ul><ul><li>Why are the neutrons even in the nucleus? </li></ul><ul><li>They have a special force, known as “STRONG NUCLEAR FORCE”, that holds the protons together, because the protons are always pushing each other out! </li></ul><ul><li>I call it “NEUTRON GLUE”! </li></ul>
  28. 28. Problems after element 82….. <ul><li>After lead, element 82, there are too many protons in the nucleus, and no number of neutrons can hold in the protons </li></ul><ul><li>The atom has gotten too big, and begins ejecting stuff to release the pressure! </li></ul><ul><li>This stuff is called radiation, or radioactivity! </li></ul><ul><li>Radioactivity is when an atom has gotten too big and it gives off stuff to relieve its pressure </li></ul><ul><li>Most atoms normally have more neutrons than protons anyway to keep the protons in place - atoms need added reinforcement! </li></ul><ul><li>So, any atom after lead is constantly giving off radiation to relieve its pressure! </li></ul><ul><li>What kind of “stuff” could an atom give off if it has gotten too big? </li></ul>
  29. 29. In summary….. <ul><li>We know that the nucleus contains… </li></ul><ul><li>Protons and neutrons! </li></ul><ul><li>And the electrons are….. </li></ul><ul><li>Orbiting around the outside! </li></ul><ul><li>Atoms that have too many protons in the nucleus (more than 82) will give off… </li></ul><ul><li>Radiation! To relieve the pressure! </li></ul>

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