Download Early History of the Atom Homework

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Early History of the Atom Homework
1. Why is Democritus’ model of the atom considered only an idea, while Dalton’s
view is considered a theory?
2. In your own words, state the main ideas of Dalton’s atomic theory.
3. State two principles from Dalton’s atomic theory that have been revised as new
information has become available.
4. To find out more about the nature of cathode rays, J. J. Thomson installed
positively and negatively charged pates. To his surprise, the beam of rays was
bent. Which way did it bend and what did this observation tell Thomson about
the nature of cathode rays?
5. What would have happened if the rays had been positively charged particles?
6. Thomson repeated his experiments using different materials for the electrodes and
a variety of gases in the cathode ray tube. In all cases, the cathode ray particles
behaved in the same manner. What did these results tell Thomson? Why was it
important to conduct these additional experiments?
7. If gold atoms were solid spheres stacked together with no space between them,
what would you expect would happen to particles shot at them?
8. When Ernest Rutherford performed his experiment, he observed that most of the
alpha particles passed straight through the gold foil. He also noted that the gold
foil did not appear to be affected. Explain these two observations.
9. Can you explain why Rutherford concluded that the mass of the gold nucleus
must be much greater than the mass of an alpha particle?
10. Rutherford experimented with many kinds of metal foil as the target. The results
were always similar. Why as it important to do this?
11. Compare and contrast Thomson’s plum pudding atomic model with Rutherford’s
nuclear atomic model.
12. Complete the following table comparing the relative charge and mass of each of
the subatomic particles.
Particle
Electron
Proton
Neutron
Relative charge
Relative mass