Flame Tests

Now that you have quantitatively measured the emission spectra for various atoms, you will have the chance to qualitatively observe the emissions of several excited metal ions.

To view the emission spectra of metal ions, energy must be applied to excite the electrons into higher energy levels. Just as electricity was applied to the discharge tubes, heat must be applied to a small amount of each metal chloride salt. You will put a spatula filled with each metal salt into a burner flame and observe the emission with your eyes.

Proceed to the flame test stations. At each station, there will be a white crystalline metal chloride salt, a burner and a spatula. Place a small amount of the solid on the spatula and heat it in the flame of the burner. Observe and record the color of the flame in your lab notebook.

Move on to the other flame test stations and repeat the above procedure until you have viewed all of the salts. Each pair of students should observe and note the emission color for Na⁺, K⁺, Ba²⁺, Sr²⁺ and Ca²⁺.

Obtain an unknown metal chloride salt from your TA. Get a spatula and clean it thoroughly with soap and water and rinse with tap water. Then rinse it well with deionized water and dry. Heat the empty spatula in the burner flame to remove any contaminants.

Heat your unknown solid in a burner flame as you did for the known metal chloride salts. Record the color of the flame from your unknown metal chloride salt and compare it to those from the known solids to determine which ion is present in your unknown solid.

Carefully rinse the spatula after it has cooled with water until any remaining solid is dissolved and return it to the community property.

Here are three examples of flames from different elements:

Back