Download Key for Light Emission Lab

Chemistry 1 - Shaver
15pts Total
OBSERVING EMISSION SPECTRA:
Name
DISCHARGE TUBES AND FLAME TESTS
Results:
In a table, record the overall light color you observe for each of the 3 discharge tubes with your
naked eye, and the lines you observe using the spectroscope. You should include each line's color
and relative brightness.
Next, do flame tests on the metal chloride solutions. As you did with the discharge lamps, record the
flame color and your observations using the spectroscope. This data should be in another table.
Objective: To observe the overall color of light and the line spectrum emitted with a spectroscope
from gaseous elements in discharge tubes and from liquid solutions burned in a flame test. Then
using these observations to make a connection between the model of the atom and an element’s
unique line spectrum.
Discussion questions:
1. What subatomic process causes atoms to emit visible, colored light when heated or put under
high electrical voltage (such as in a gas discharge tube). Briefly describe.
(2pts)-The electrons become excited by the heat or bombardment of electrons (kinetic energy
transferred) and then shortly thereafter fall back down to their ground state. It is then –
“relaxation” - that they emit that specific quantity of energy in the form of radiation (light). This
specific quantity or packet of energy can be called a photon.
2. Why do atoms emit a line spectrum (only specific colors of light) when excited, instead of a
continuous spectrum?
(2pts) This deals with the energy absorbed or released is “quantized”. Meaning only specific
amounts of energy can be released. An electron cannot release any quantity of energy but rather
only certain quantities that are dictated by the spacing between energy levels in the atom.
Atoms emitting light deal with individual electrons releasing various frequencies of light based on
the energy level drop.
3. In a sentence or two, what determines the color of a given line in a line emission spectrum?
The energy released when the atom goes from the excited to relaxed state is directly related to a
specific frequency and thus wavelength. You can then compare the wavelength to the
electromagnetic spectrum (listing the wavelength range for each type of radiation).
If this color is within the visible portion of the electromagnetic spectrum, we perceive this frequency
and wavelength as a specific color. If it is outside this range, we will not detect anything.
4. Explain the relationship between the macroscopic observations you made: the overall color of a
lamp or flame test versus the emission spectrum as viewed through the spectroscope?
The overall color we saw related to the individual line spectrum because it was a combination of the
lines emitted and their relative intensities that gave the overall color.
5. Why does each element have its own unique or characteristic spectrum? (In other words, why does
the spectrum of hydrogen look different than that of helium or mercury?) What does this imply
about energy levels in different elements?
There is unique spacing between the energy levels in different elements.
Go back to the start of your write-up and write a purpose statement. It should be no longer than
three sentences, and should summarize the point of this lab in terms of what it taught you about
atomic structure.
Objective: To observe the overall color of light and the line spectrum emitted with a spectroscope
from elements in gas discharge tubes and from flame tests. Then using these observations to make
the connection between an element’s unique line spectrum and the model of the atom.