Purpose
To demonstrate that chemicals with similar properties can still have different electronic structures by showing the spectra produced by different ions in a flame.
Materials
- Methanolic salt solutions (sodium, lithium, potassium, calcium, copper)
- Spray bottles
- Bunsen burner (with a Meeker burner attachment)
- Watch glasses
- Spectroscopic grids (for small classes)
- Water (for cleaning spray bottles)
Procedure
Preparing the Spray Bottles
- Check Spray Mechanism:
- Ensure spray bottles are functioning properly. Clean out any salt buildup by spraying water through them for a few minutes if necessary.
Conducting the Flame Test
- Using the Spray Method:
- Fill spray bottles with methanolic solutions of the selected salts (Na, Li, K, Ca, Cu).
- Always point the spray away from the class.
- Spray through the Meeker burner to ignite the solution, creating colorful flames.
- Using Watch Glasses:
- Alternatively, place samples of the salts (preferably chlorides except for copper, which uses sulfate) on watch glasses.
- Add a few squirts of methanol to each sample and ignite to create a standing flame.
Observing the Spectra
- Spectroscopic Grids:
- In smaller classes, use small squares of c-spectra to approximate a spectroscope.
- Have students observe the spectra near the flame, which works best in a dark room.
Conclusion
This experiment effectively illustrates the concept of electronic structure differences among various ions, despite their similar properties, through the visual display of colored flames produced by different metal salts.