Mr. Sandoe
3/18/1915
Democritus and Ernie Rutherford
Max Planck and Niels Bohr were both big contributing scientists to the studies of electrons and energy. They concluded that electrons can only exist in certain orbitals around the atom and that these orbitals have very specific energy values. For an electron to move from one orbital to another orbital, it must either absorb a specific amount of energy
(moving from ground state to excited state) or it must emit a specific amount of energy
(falling from excited state to ground state). The purpose of this lab was to explore the work done concerning electrons by Max Planck and Niels Bohr. This was done by observing the electron transitions of various metals using a flame test.
Starting at one of the stations in the lab, a Bunsen burner was attached to the gas jet.
One of the wooden splints provided was dipped into a beaker of distilled water. The moist end of the splint was rolled in the provided crystal that was on a watch glass. The Bunsen burner was then lit with a striker and the crystal-coated end of the wooden splint was inserted into the flame. Descriptive observations about the flame’s color were recorded.
The splint was then cooled under running water and disposed of in the trash can. The same process was repeated for all ten samples in the lab.
Strontium Chloride
Barium Chloride
Sodium Chloride
Copper (II) Chloride
Cobalt Chloride
Unknown 1
Unknown 2
Lithium Chloride
Calcium Chloride
Potassium Chloride
Sharp, red/orange
Soft, light lime green
Pale orange
Blue-ish teal
Same flame orange with white sparks
Soft, light lime green
Sharp, red/orange
Strong, sharp pink
Bright orange
Strong, deep purple
Approximated Wavelength (nm)
Emitted From the Chemical
680 nm
570 nm
620 nm
540 nm
625 nm
570 nm
680 nm
740 nm
630 nm
410 nm
After analyzing the data from this lab, it can be concluded that unknown 1 was barium chloride and unknown 2 was strontium chloride. Both unknown 1 and barium chloride produced soft, light lime green flames that were very similar in color (around 570 nm). Both unknown 2 and strontium chloride resulted in sharp red/orange flames that were very comparable (around 680 nm).
The purpose of observing electron transitions and exploring Planck’s and Bohr’s work was fulfilled by the lab work. Electron transitions were viewed, as the various colorful observations give evidence for this. Electrons from the metals used in the procedure

absorbed energy from the flame, causing a jump to an excited state. The excited electron then emitted this energy when it fell back to its original ground state energy level. The energy emitted was within the visible spectrum, allowing us to see it. Distinctively different colors show evidence that energy levels contain a certain energy value, and that the electrons can’t exist between the levels. They must move from level to level without existing between them, so they cannot emit or absorb a random amount of energy but rather specific energy values.
A major source of error resulted when a lab group dropped an unknown compound into one of the Bunsen burners, causing the flame to burn ruby red no matter what compound was being tested. No other procedural errors were made during the lab. The lab has some inherent error in that the data collected is all subjective depending on the viewer.
Two viewers of the same flame may describe the flame color differently, leading to some inaccuracy and difficulty in describing results.
1. Which ion in the compound causes the flame to change color? Explain the
reasoning for your answer.
The cation must be the ion responsible for the color change because the anion
(chloride) stays consistent for all of the compounds used in the lab. It doesn’t make sense for the consistent ion (anion) to be responsible for the changing color of the flame.
2. On the atomic level, what is happening to the electron that causes the flame to be
a different color?
The electron first absorbs energy from the flame. This causes it to jump to an excited state. It then falls back down to its original ground state energy level.
Energy must be emitted to fall to the ground state. This energy that is emitted is in the visible spectrum and is responsible for the flame being a different color.
3. What are some difficulties or problems with using the flame test as a qualitative
tool? What are some of the advantages of using it?
One problem with using a flame test as a qualitative tool is that the data can be very subjective to the viewer. Not everyone’s description of a flame will be consistent. The flame test is, however, very cheap, quick, and easy to complete.
4. Why was distilled ( or de-ionized) water used to moisten the cotton swab instead of
tap water?
Distilled water is also called de-ionized water, meaning it does not contain any ions.
Tap water must contain many ions in it. Since the flame test depends on an ion (the cation) to change the flame’s color, using water with various unknown ions in it could alter the color of the flame and not provide the best results possible.
5.
Explain at least one thing you can think of that would help this lab be come reliable
and accurate.
One suggestion for increasing the validity of the lab work would be to implement the use of a tool that could give an exact measurement of the wavelength of the light that was seen. This would remove subjectivity and variety in color descriptions.