SWB Cp II Atoms

Atoms

and

Their Structure

Models of Atomic Structure (Instructor’s Copy)

Objectives:

· To demonstrate or discuss how scientific knowledge is acquired, by engaging in an active, integrated learning experience

· To state, and demonstrate with examples, the importance of experimentation used to test predictions and support or refute hypotheses

· To describe the currently accepted model of the atom and explain why this model is preferable to other models; to describe and explain previous models.

Materials: “Rutherford” Boards (Please do NOT look at the underside of the “Rutherford” boards.), marbles

Instructions:

1. Find an unobstructed area for your group of 5 or 6 to work. You may use the hallway nearby if you will not disturb other classes.

2. Standing almost 2 meters away from the board, roll marbles at the board, one at a time, until you have rolled 30 marbles. Vary the angle at which you roll the marbles

3. Prior to rolling the next marble, observe the path of each marble and record whether the marble passed straight through under the board, was deflected slightly (up to 30o), or was deflected substantially (more than 30o). Estimates are close enough

4. Record your data in the chart below

5. Put your data on the class chart (overhead) and record the total for the class data

6. Record percentages in the Data Table and answer the questions.

Data Table:

Group Data / Group
Percentage / Class Data / Class
Percentage
# passing straight through / ______of 30 / ______of ______
# of slight deflections / ______of 30 / ______of ______
# of large deflections / ______of 30 / ______of ______

Analysis: (Questions, Predictions)

1. Rutherford shot alpha particles at thin gold foil. In this activity, what did you use to represent the alpha particles?

marbles represented the alpha particles

2. In this activity, what did you use to represent the thin gold foil?

The “Rutherford” boards represented the gold foil

3. Rutherford expected all alpha particles to pass through the gold foil undeflected.

(A) What percentage of your “alpha particles” passed through undeflected?

Varies, usually about half.

(B) What percentage of your “alpha particles” were deflected either slightly or substantially?

Varies, may be close to one half. For Rutherford, it was 1 in 1000

4. Based on your data, describe the underside of the Rutherford board. (You should NOT have looked at it yet.)

Some obstruction (nails) prevents some marbles from passing through undeflected.

5. Look at the underside of the Rutherford board. Was your description above essentially correct? Explain.

6. How is the underside of the Rutherford board analogous to the gold foil (or parts of the foil)?

The nails under the Rutherford board to analogous to the nuclei in the gold foil. Both prevented particles (marbles/alpha particles) from passing through undeflected.

7. Modify Thomson’s model of the atom based on your simulation of Rutherford’s experiment. Explain the modifications that are included in Rutherford’s model of the atom.

The negative electrons are still present, but there is a nucleus of relatively large mass present based on Rutherford’s experiment.

JA answers in red (To hide sketches in last column, Uncheck “Drawing Objects” under “Options” when telling to “Print”

Page 4

Atoms-Rutherford model.do 1, 01227 12/29/00 10:48 AM