Inquiry in the Natural World Student Guide – Spring 2005

Topic 7 – Atoms: Dalton and Beyond

Topic Objectives

1. Understand the principles of the Mechanical Philosophy, appreciate when and why it originated, and be able to describe specific views held by Descartes, Boyle, and Newton.

2. Know how Dalton proposed to determine the relative atomic weights of elements, based on the law of constant proportions and his own “rule” of greatest simplicity.

3. Understand Gay-Lussac’s method of determining the combining volumes of gases, and appreciate why Dalton rejected Gay-Lussac’s ideas and how Avogadro solved the problem.

4. Appreciate how Mendeleev organized the known elements into a “Table of Elements” and how that table was modified to produce the modern periodic table.

5. Know how J. J. Thomson discovered the first subatomic particle, and the model of the atom that he constructed to explain his observations.

6. Understand how Rutherford’s gold-foil experiment lead him to develop a new model of the atom and how this atomic model differed from Thomson’s previous model.

7. Appreciate the evidence that led Bohr to modify Rutherford’s of the atom and how Bohr’s model treated electrons as having properties of waves as well as particles.

8. Appreciate Heisenberg’s Uncertainty Principle and how it relates to our knowledge of the sub-atomic world.

9. Be able to describe the structure of the atom using the currently accepted model.

Wednesday, March 16 Reading Assignment: entire Chapter 14 in textbook

Questions for Discussion:

1. What aspects of the earlier (Aristotelian, alchemical, neo-Platonist) ideas about matter proponents of the Mechanical Philosophy object to? What basic characteristics of matter were they willing to accept?

2. How did Newton’s conception of matter differ from Descartes’, and from Boyle’s?

Friday, March 18 Reading Assignment: entire Chapter 15 in textbook

Questions for Discussion:

1. How did Dalton describe atoms in general, and what additional ideas did he have about atoms of a single element?

2. What was Dalton’s “rule” of greatest simplicity? How did this assumption lead to Dalton’s first relative atomic weights?

3. Why was Dalton not convinced by Gay-Lussac’s interpretation of the data on combining gas volumes? How did Avogadro explain this discrepancy between expected and observed product volumes?

Monday, March 21 Reading Assignment (for Big Lecture): use the following websites.

American Institute of Physics. J. J. Thomson. Accessed 12 Mar 2005.

<http://www.aip.org/history/electron/jjthomson.htm>. (follow the links to all 5 pages of the exhibit)

Author unknown. Rutherford’s Experiment – Part II: The Paper of 1911. Accessed 12 Mar 2005. <http://dbhs.wvusd.k12.ca.us/webdocs/AtomicStructure/Rutherford-Model.html >.

Science Joy Wagon. 1999. Models of Atom. Accessed 12 Mar 2005.
<http://regentsprep.org/Regents/physics/phys05/catomodel/default.htm>. (ignore the formulas on the Bohr page)

Thomas Jefferson National Accelerator Facility - Office of Science Education. All about Atoms: Protons. Accessed 12 Mar 2005. <http://education.jlab.org/atomtour/proton.html.>