SAM Teachers Guide
Spectroscopy
Overview
Spectroscopy is a powerful tool for identifying atoms. An atom’s spectrum is like its
fingerprint—unique to that particular kind of atom. Students explore the relationship
between an atom’s energy levels and its photon emissions. They explore the different
ways an atom might be excited. Finally, students compare patterns of spectral emissions
in order to identify the atomic constituents of matter.
Learning Objectives
Students will be able to:
 Determine that the frequency of a photon is determined by the difference of
energy levels between the states of an excited electron.
 Add energy and excite atoms.
 Analyze photon emissions and identify atoms that emit them.
 Determine that atoms can absorb photons of specific frequencies.
 Explore emissions spectra, and identify atoms by their spectrum.
Possible Student Pre/Misconceptions
 Light exists only where it can be seen.
 Different colors of light are different types of waves.
 Light is a mixture of particles and waves.
 There is no interaction between light and matter.
 The addition of all colors of light yields black.
Models to Highlight and Possible Discussion Questions
NOTE: Many concepts discussed in Spectroscopy are introduced in the Excited
States and Photons activity. If your students have not done that activity, we highly
recommend you review the activity prior to running Spectroscopy and discuss the
model and concepts with your students.
Models to Highlight:
• Page 1 – Frequency and color
o Highlight how the model represents invisible photons such as
infrared and ultraviolet as black while visible photons are shown in
the colors that correspond to their frequencies.
•



o Link to other SAM activities: Excited States and Photons. The
activity introduces the relationship between atomic structure,
energy levels, and excitation of atoms.
Page 2 – Exciting an atom
o Demonstrate for your students how to excite an atom by dragging
the white circle from the ground state energy level to an excited
state on the energy level diagram.
o Highlight the relationship between the location of the circle on the
energy level and the photons that are emitted.
o Link to other SAM activities: Atomic Structure. Review the
structure of an atom and how it changes when an electron jumps to
an excited state.
Page 4 – Which atom emitted which photon?
o Remind students that each atom has a unique emission of photons
based on the atom’s energy levels.
Page 5 – Absorbing a photon
o Have students describe their solutions to the challenge. Reinforce
that for atoms to absorb photons, at least one pair of excited states
must have the same energy difference as the photon.
Page 6 – Emission spectrometer
o Highlight the connection between the photons and the color lines
that appear in the spectrometer below the model.
Possible Discussion Questions:
 For a photon to be absorbed what must be true about its energy?
 What best describes the relationship between frequency and energy of
light?
 A yellow laser is shown to pass through gaseous atoms without being
absorbed. What could be done to test if photon absorption might occur at
a higher energy?
 How does the model represent an emission spectrum?
 How might adding more atoms affect the emission spectrum? How might
more energy levels affect the emission spectrum?
 Demonstration/Laboratory Ideas:
o Have students use a prism and a diffraction grating to view a
variety of light sources, including incandescent and fluorescent
bulbs and spectrum tubes for different elements.
Connections to Other SAM Activities
In Spectroscopy students explore how atoms give off different patterns of light energies
and wavelengths of light, called photons. Excited States and Photons supports
Spectroscopy because students are introduced to photons and how excited atoms
produce photons. Atomic Structure is a prerequisite as it gives students a fundamental
understanding of how an atom’s structure changes when an electron moves into an
excited state and, thus, into a different orbital. Although orbitals are not addressed
directly in Spectroscopy, if students are familiar with them, they will help explain what
is going on in our more abstract representations of excited atoms.
Spectroscopy supports two activities, Chemical Reactions and Energy and Harvesting
light for photosynthesis. One section of Chemical Reactions and Energy is focused on
photochemistry in which light can break bonds or light can be given off as bonds form.
Harvesting light for photosynthesis explores the way light interacts with matter in
biological systems. For example, molecules such as chlorophyll will absorb only certain
frequencies or photons. Spectroscopy helps students understand why different atoms
and molecules can absorb and emit different wavelengths of light.
Activity Answer Guide
Page 1:
1. What color light has the highest
frequency?
(d)
3. Take a snapshot of the energy level
diagram just before the atom emits a blue
photon and insert it below.
2. Which photon has the lowest amount of
energy? (a)
Page 2:
*Sample Snapshots: Other snapshots may
answer the questions.
1. Take a snapshot of the model just before
the atom emits a blue photon and insert it
below.
Energy levels before blue photon was emitted.
4. Take a snapshot of the energy level
diagram just after the atom emits a blue
photon and insert it below.
This snapshot shows an excited atom right
before the photon is emitted.
2. Take a snapshot of the model just after the
atom emits a blue photon and insert it below.
Energy levels after blue photon was emitted.
5. Which energy levels (refer to them as the
top, middle and bottom one) were involved in
making the blue photon? In other words,
what state was the atom in before it emitted
the photon and where did it end up?
The electron went from the middle energy level
to the ground state (bottom) energy level when
the photon was emitted.
This snapshot shows the blue photon.
Page 3:
1. Heat the model until several atoms are
excited. Then let it run. Describe what
happens to the atoms.
The heat excites the atoms. The excited atoms
emit photons. Some collisions also excite atoms.
The atoms cool down until they no longer have
enough energy during collisions to excite an
atom in the system. After that the atoms do not
emit photons so they don't lose energy.
3. Reset the model, and do not heat up the
model. Adjust the energy levels to see if you
can get any photon emitted. Write down what
you need to do below.
Answers may vary. I lowered the bottom energy
level from –3.30 eV to about –3.80 eV. When
this was done there was enough energy in the
system to excite the atoms to the lowest excited
state.
Pictures will vary. The purple atom in the top
right of the model is about to absorb the energy
from the photon.
2. Fill in a snapshot image below to show
the model after a photon is absorbed by a
purple atom:
Page 4:
1. The picture on the left shows an infrared
photon. Run the model until you see a
photon like this, then stop the model and run
it back and forth frame by frame to figure out
which type of atom emits this type of photon.
Write your answer below.
The green atom emits the infrared photon.
2. Run the model until you see a blue
photon. Stop the model and run it back and
forth. Which type of atom emitted the blue
photon?
The purple atom emits the blue photon.
Page 5:
1. Fill in a snapshot image below to show the
model before a photon is absorbed by a
purple atom:
Pictures will vary. The purple atom has
absorbed the photon and is now in an excited
state.
3. In the space below, explain in your own
words what you had to do to make the blue
atom emit photons that the purple atoms
could absorb.
Answers will vary. I moved the middle energy
level so that it was at -4.00 eV. In this way it
represented the same energy difference from
the ground state to the first excited state as the
purple atom does from the ground state to its
first excited state. The difference was 1.00 eV.
Page 6:
1. The picture above shows a spectrum with
six lines in it, three of them visible, one
infrared, and two ultraviolet. How many
energy levels do you think the atom had that
made this spectrum? Experiment with the
model and see if you can make a spectrum
with six lines. Check off below how many
energy levels it took. (b)
Page 7:
1. Paste a snapshot of Type-1 atoms'
spectrum here.
2. Paste a snapshot of Type-2 atoms'
spectrum here.
Page 8:
1. A certain atom has two excited states.
How many spectral lines can it produce at
maximum?
(c)
2. Is it possible for two different types of
atom to have exactly the same spectra but
not have exactly the same energy levels?
(a)
3. A scientist measured the spectrum of a
gas supposedly composed purely of Type-C
atoms, but he found the spectrum revealed
that the gas was contaminated. Can you
identify which type of atoms could have
possibly contaminated the gas? (The box in
the above image shows the spectra of four
types of atoms: A, B, C and D. The spectrum
below the box shows the result he obtained.)
(a) (c)
3. Paste a snapshot of Type-3 atoms'
spectrum here.
4. Of the following transitions between the
energy levels shown in the right graph,
which results in photons with the lowest
possible frequency?
(d)
4. Paste a snapshot of Type-4 atoms'
spectrum here.
5. Paste a snapshot of the unknown atoms'
spectrum here.
6. Which type is most likely the unknown
atom? (b)
SAM HOMEWORK QUESTIONS
Spectroscopy
Directions: After completing the unit, answer the following questions to review.
1. Describe the relationship between energy, frequency and color of light.
2. To the left is a picture of one particular atom’s energy levels. How many
spectral lines can it produce at maximum? Draw the transitions in energy
levels and explain your answer.
3. In the following transitions between energy levels, which one would result in photons with
the highest possible frequency? Why? Explain your answer.
4_______
3_______
2_______
1_______
4. In chemistry class, you learn that excited mercury atoms emit ultraviolet light, so you set out
to build a new type of light bulb to take advantage of this phenomenon. You eventually develop
a system that allows you to produce excited mercury atoms within a glass tube. The only
problem is that the light produced is still ultraviolet. How might you convert your light bulb in
order to convert your ultraviolet light into visible light?
SAM HOMEWORK QUESTIONS
Spectroscopy – With Suggested Answers for Teachers
Directions: After completing the unit, answer the following questions to review.
1. Describe the relationship between energy, frequency and color of light.
The color of light is determined by its frequency. Photons are particles of light that carry energy. The higher the
frequency of light, the more energy the photon carries.
2. To the left is a picture of one particular atom’s energy levels. How many
spectral lines can it produce at maximum? Draw the transitions in energy
levels and explain your answer.
There are six different transitions that can be made when moving from higher to lower
energy levels. This includes transitions from the three excited states to the ground state and
from exited states to lower energy excited states. Each transition has a corresponding
frequency of light emitted (spectral line).
3. In the following transitions between energy levels, which one would result in photons with the
highest possible frequency? Why? Explain your answer.
4_______
3_______
2_______
1_______
The transition from 41 would result in photons with the highest frequency because the greatest amount of energy
is released. The energy levels are farthest apart.
4. In chemistry class, you learn that excited mercury atoms emit ultraviolet light, so you set out
to build a new type of light bulb to take advantage of this phenomenon. You eventually develop
a system that allows you to produce excited mercury atoms within a glass tube. The only
problem is that the light produced is still ultraviolet. How might you convert your light bulb in
order to convert your ultraviolet light into visible light?
You could coat the inside of the bulb with a substance that absorbs the high-energy UV photons and emits less
energetic, visible photons and/or heat.