Beacon Lesson Plan Library

The Three E's - Exciting Energetic Electrons

Coleen Pemberton

Description

Students correctly record electron configurations for select cations and then perform flame tests on salts containing those ions. Students observe results with spectroscopes and prepare a lab report.

Objectives

The student knows that the electron configuration in atoms determines how a substance reacts and how much energy is involved in its reactions.

Materials

-Notebook paper
-Pencil
-Colored pencils
-Bunsen burner
-Spark lighter
-Ethyl alcohol
-Distilled water
-Four pyrex bowls (approximately 30 mL)
-Inorganic salts: sodium chloride, potassium chloride, barium chloride, calcium chloride, copper chloride, strontium chloride
-Presoaked wooden splints
-Student spectroscopes
-Film canisters (number based on number of samples used)
-Prepared overhead transparency of electron configurations and energy changes

Preparations

1. Obtain four pyrex glass bowls, ethyl alcohol, and salts of your choice based on lab procedure and materials above.
2. Perform demonstration from above procedure to ensure appropriate amount of alcohol and salt are being used and you know the colors to anticipate.
3. Make any adjustments necessary to assure that students are able to view colors emitted from ignited salts.
4. Prepare lab baskets for students (attempt to have one basket for every two students) by placing selected inorganic salts in small sealed-up, labeled containers such as film cases. If containers are filled about 1/3 full they can be reused several times before restocking is needed. Strontium and lithium chloride will not store well in this manner and may need to be emptied and replaced.
5. Place the number of wooden splints needed (dependent on number of students) in deionized water the night before and be sure that a waste container is available for the lab session.
6. If already stocked lab stations are not available, then a method of obtaining and returning additional materials should be planned ahead. This will vary with classroom/lab facility.
7. If students are to dispose of any waste, be sure marked containers are available and designated.
8. Verify before lab time that all safety requirements are met and aprons and goggles are available.
9. Have a sample rubric prepared.

Procedures

Preparation of lab baskets can be done ahead of time by placing selected inorganic salts in small seal-up labeled containers such as film canisters. If containers are filled about 1/3 full, they can be reused several times before restocking is needed. Strontium and lithium chloride will not store well in this manner and may need to be emptied and replaced. The teacher should also place the number of wooden splints needed (dependent on number of students) in distilled water the night before and be sure that a waste container is available for the lab session. If already stocked lab stations are not available then, a method of obtaining and returning additional materials should be planned ahead.

1. Teacher puts on lab coat and goggles for demonstration.

2. Teacher places four 25 mL pyrex bowls each containing 5 mL of ethyl alcohol on the demonstration table.

3. To each of the four containers, the teacher adds approximately 0.5 g of any four of the six salts to be tested later by students. A good variety is potassium chloride, sodium chloride, strontium chloride, and copper chloride.

4. Teacher has a selected student dim the lights as he/she strikes a match and lights the contents of the four containers. As a safety precaution, be sure students are at least two feet away from demonstration table.

5. While the students notice the four distinct colors, the teacher queries students for the cause of the flame colors being viewed.

6. Teacher reviews importance and usage of electron arrangement and energies.

7. Students write electron configurations for the following cations: sodium, potassium, strontium, barium, calcium, and copper

8. Students write electron configuration for the chloride anion.

9. Students compare their configurations with overhead diagrams.

10. Teacher queries students about similarities and differences in configurations.

11. Students view computerized change in energy levels for the selected ions (if this is available) If a program is not available, a board diagram can be used showing the rise and fall of electrons as they absorb and lose energy.

12. Students go to their lab stations where a basket containing six known salts and two unknown salts is located.

13. Students use presoaked wood splints and touch the splints gently to the salts in each supplied container. Students place samples of the metallic chlorides into the bunsen burner flame and observe the color emissions.

14. Students record descriptions of each flame test using words and/or colored pencils to assist them in their description.

15. Students place used wooden splints in location designated by teacher.

16. Students repeat flame testing procedure but view the color pattern as seen through a spectroscope. Use colored pencils to show bright line spectrum viewed.

17. Students place second set of wooden splints in location designated by teacher.

18. Students verify with teacher that they have correctly identified their unknown samples. If unknowns are not correct, student and teacher will discuss sources of error which may then be incorporated in final laboratory report.

19. Students verify that all containers are securely capped, work area is clean, and student spectroscopes are returned to designated location.

20. Students prepare laboratory report according to established format.

Assessments

Before beginning the lab activity, conduct a question/answer or discussion session with students about what allows us to see so many different colors of light. Include colors from fireworks, light bulbs, and sunsets. Explain to them that after the lab is finished, there will be another discussion and a report prepared to share their discoveries about the nature of light.

After the lab, students will have another discussion about the nature of light and then prepare a written laboratory report which should include a data chart showing the colors correctly identified for the inorganic salts selected by the teacher.

Extensions

Teachers may want to include an unknown salt for evaluation based on data collected. Electron configuration writing and electron energy absorbance and emission.

Web Links

Web supplement for 'The Three E's - Exciting Energetic Electrons'
Professor Quester Answers Questions on Electricity

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