Robert Hatch

SUBTOPIC:

 Scientists who Created the New Physics and New Theory of the Atom

OBJECTIVES:

The students will:

1. trace the sequential process of the developing theories of atomic structure in the early 20th century
2. show, in historical development, how scientists “know” things, how experiments are set up and how interpretations are drawn from them
3. illustrate the successive models of the atom from the planetary model to the quantum mechanical model
4. describe, using the development of quantum theory, the manner in which scientists share information and build upon the work of each other
5. show, by the debate between particulate and continuous matter, the active process of scientific disagreement and the search for a better understanding of universal laws
6. describe the final (Einstein/Bohr) debate, and how there are different interpretations of the same sets of data

Background Information

Many people contributed to the concept of the atom. They came from various countries and contributed their varying expertise to the major problem of the day–how to explain the atomic phenomenon with the theories of classical physics. From the struggle came a new theory of the atom and a new physics–quantum physics. 

When scientists review the data from an experiment, many factors, besides their scientific knowledge (such as background, culture, and beliefs) influence their interpretations. These interpretations are usually indicative of the philosophy of the scientists.

The key scientists to consider for this unit are:

1. Ernest Rutherford–discovered the nucleus of the atom and developed the planetary model of the first structure of the atom.
2. Erwin Schrödinger–developed the equations that define the wave-like traits of atomic behavior as deduced from spectral analysis.
3. Werner Heisenberg–devised the uncertainty principle which defined mathematically that any measurement of a particle’s position and momentum cannot be determined concurrently. Matter can either be described as a wave or a particle, but not both simultaneously.
4. Niels Bohr–perceived the problem with Rutherford’s planetary model of the atom, and used Planck’s quantum theory to describe the phenomenon of electron movement. He used Heisenberg’s uncertainty principle to redefine further electron motion in the atom. His interpretation is called “complimentarity,” as it used the mutually exclusive concepts of wave particle to reach the maximum possible understanding of the quantum model of the atomic theory.
5. Albert Einstein–is responsible for the theory of relativity which redefined mass, energy, motion, space, and time. When this theory was joined with theories and knowledge of the atom, a new age in chemistry and physics dawned.

ACTIVITY #1:

Presentation of Results

            1 week: 2 periods research in library, 3 periods presentations

PROCEDURE:

1. Divide class into small groups. Assign each group to report on one of the key figures of 20th-century physics-chemistry to research. These should include the six individuals listed above and any others of interest.
2. Each group report should include the following information about each man:
   1. family background
   2. individual personality 
   3. educational views
   4. approach to work
   5. how each man viewed the results of his own accomplishments in science
   6. how society viewed each man’s scientific accomplishments
   7. the philosophy of each man and its influence upon the conclusions he drew from his data
3. After topics have been researched, compile small group reports with members of a group sitting at the same table (perfect for science labs). 
4. An “expert” from each group should exchange the information he has learned with the other groups. In this way, all students are informed, and all students have the responsibility for participation as each member of the group gets a turn to be the “expert.”

ACTIVITY #2:

Debate Controversial Issues 

           1 class period per issue

PROCEDURE:

1. After class presentations on the important scientific figures, follow up with a debate on the controversial issues that grew out of their discoveries. Listed below are some possible situations to debate:
   1. Heisenberg vs. Schrödinger
      Particle vs. wave theory of energy and the atom
   2. Rutherford vs. Bohr vs. Heisenberg
      Model vs. No-model of the atom
   3. Planck-Shrödinger vs. Bohr-Heisenberg
      Quantum physics would/would not be resolved with classical physics
   4. Bohr vs. Einstein
      Nature may be more complex than human reason  vs.  Nature is rational, logical, and consistent, so there must be one answer to all

ACTIVITY #3:

Probability Model for the Hydrogen Atom

             2 class periods (1 for collecting data, 1 for analyzing the data)

MATERIALS:  

DART BOARD AND DARTS, ATOM TARGET, COMPUTER WITH SPREADSHEET PROGRAM OR OTHER MEANS OF GRAPHING DATA COLLECTED

PROCEDURE:

This experiment is for pairs of students or small groups of no more than four.

1. Fix target to a spot on the floor.
2. Have a student stand on a chair or stool with the target below on the floor.
3. Have student extend an arm holding the dart out from his/her body so that it is about two meters above the target.
4. The student must drop (not throw) the dart in such a way as to try to hit the bulls eye.
5. Have the next student retrieve the dart and repeat steps 2-4.
6. Repeat procedure until 100 drops have been made. Do not count drops that do not stick inside the largest circle.
7. Count the number of hits in each ring by the area of the ring. Record this in the data table.
8. Divide the number of hits in each ring by the area of the ring. Record this number as hits per unit area in table.
9. Each group should plot the radial probability and hit density graphs from their data.
10. The class data can be compared to the actual probability for the hydrogen atom structure.

Note: This activity could serve as an introduction to the study of atomic structure and periodicity to be developed as a unit by the teacher for chemistry classes. For the physics class, the exercise may be used to introduce quantum mechanics, and for the history class, it may be used to link scientific achievements to the philosophical, historical, or political views of that time.

Bibliography

Cline, Barbara L. Men Who Made a New Physics. Chicago: Chicago UP, 1987.

Dorin, Henry, et al. Chemistry: The Study of Matter. Englewood Cliffs, NJ: Prentice Hall, 1989.

Gamow, George. Great Physics form Galileo to Einstein. New York: Dover, 1961.

Jungk, Robert. Brighter Than a Thousand Suns: A Personal History of the Atomic Scientists. New York: Harcourt, Brace, Jovanovich, 1958.

Masterson, William L. et al. Chemistry. New York: Holt, Rinehart, Winston, 1980.