Discovering the Atom
Instructions: Go to each website and use the information and animations to answer the questions. This is an exploration....explore. The links should work.....if they do not, try cutting and pasting the address into your browser. If you come across other interesting sources, please share. The questions should be
answered in full detail, on a separate sheet of paper or in the MOODLE if your teacher has assigned it there. Your textbook
also contains useful information on the history of the atom.
1 and 2:
1a. According to Democritus,
what is the composition of matter?
1b. What is the root of our word "atom" and how is this root misleading?
2. The Greeks believed
that fire was a state of matter. How did atomists describe fire?
3 and 4:
3. What are the five
main ideas of Dalton's theory? What idea compromised the acceptance of his work?
4. Which of the basic
ideas of Dalton's Atomic Theory is an extension of what the Greeks believed
5 and 6:
5. How did William Crookes determine the nature of the beam in cathode
6. What did he conclude from his experiment?
7, 8 and 9:
7. How did Thomson use the cathode ray tube in his research?
8. What did Thomson conclude based on his research?
9. How did Thomson’s findings revise Dalton’s Atomic Theory?
Millikan's Oil Drop Experiment:
Visit the four sites above and then go back to the simulation at the last link (webassign.net) and complete 10-13.
10. Press the bulb of the atomizer and observe. Describe what happens to the oil drops.
11. Now turn on the circuit, by pressing the button on the bottom right so that it goes from reading OFF, to reading ON. Spray the atomizer again. Describe the behavior of the drops.
12. Now play with the voltage by changing the potential difference. Spray the atomizer and observe. Move the voltage up and down and observe the drops. Record the voltage that makes some of the drops stay suspended in the middle of the apparatus.
13. Based on the interaction between the oil drops and the electric field,
what did Millikan conclude?
14. Describe and sketch Thomson’s model of the atom. What is wrong with the picture presented on the www.iun.edu page?
15. Go to the micro.magnet.fsu site. What do you observe when the slit width is adjusted to 4.0 nm?
16. How did Rutherford’s experiment disprove Thomson’s model
of the atom?
17. What new model did Rutherford propose? Sketch it.
18. Which subatomic particle did James Chadwick discover? Compare its
mass to that of a proton.
19. Who was credited with the discovery of X-rays?
20. What important discovery did Becquerel make upon examining a piece
of pitchblende wrapped up in paper? (Pitchblende is a source of uranium)
21. What two elements did the Curies discover?
22. Becquerel was credited with discovering radioactivity, the spontaneous
emission of radiation by a material. He also noticed that both X-rays
and the radiation emitted by uranium had strong effects on photographic film, yet they are not the same. What
important difference between radiation emitted by uranium and X-rays led
him to this conclusion?
Return to top