Lab Activity #7: Virtual Atomic Energy Levels
Objective:
 To observe how the lines in the emission spectrum of hydrogen are related to electron energy levels.
Pre-Lab:
Recall that when light from the sun or light from an incandescent bulb is passed through a prism or diffraction
grating, it is separated into its component wavelengths (See Figure 1).
Figure 1
Since white light contains light of every wavelength, a continuous spectrum, containing all wavelengths of light
of visible light is produced. A rainbow is an example of a continuous spectrum seen when droplets of water in the
atmosphere act as prisms (see Figure 2).
Figure 2
However, when light from a hot gaseous element is passed through a prism, an entirely different spectrum is
observed (see Figure 3).
Figure 3
This spectrum, called an emission spectrum or bright-line spectrum, contains only a limited number of lines,
each representing a different wavelength. The emission spectrum of hydrogen, the simplest atom, is shown in
Figure 4. Notice that only 4 lines are observed.
Figure 4
In this lab, you will discover the origin of these lines and what they tell us about hydrogen's energy levels.
Procedure:
1. Start the Neon Lights and Other Discharge Lamps simulation (Run Now, Open).
2. A battery provides a source of electrons and the region of blank space represents the gas tube. There is only
one hydrogen atom in the tube. The atom is labeled "1." Look at the Energy Level Diagram to the right.
 What does the "1" signify?
3. Choose "Slow Motion" in the Options box and click "Fire Electron."
 What happens to the electron in the hydrogen atom when an electron collides with it?
 What is released by the atom (see the Legend)?
 What ultimately happens to the electron in the hydrogen atom?
4. Choose the "Multiple Atoms" tab and check the Spectrometer box under Options. Wait for hydrogen's
emission spectrum to populate (feel free to increase the Continuous slider bar) and then record it below.
 Compare/contrast this spectrum to the one shown in Figure 4.
5. Click the One Atom tab.
6. Experiment with changing the voltage provided by the battery.
 What is the relationship between the amount of electrical energy provided by the battery (energy at
collision), the amount of energy between two energy levels and whether an electron will be excited?
7. Set the Battery to 30.0 V and continuous @ 50%.
8. Click Slow Motion and try to see the relationship between the energy level transition and the type of radiation
emitted.
 To what energy level do electrons have to relax in order to produce UV light?
 Visible?
 IR?
9. Click Slow Motion and determine the exact energy level transition that produces the
 Red line:
n = ___ to n = _____
 Blue-Green Line
n = ___ to n = _____
 Blue line
n = ___ to n = _____
 Violet line
n = ___ to n = _____
10. Reset/reload the simulation. Choose Configurable as the atom type.
11. Using 2 energy levels, change the size of the energy gap between them and fire single electrons at the atom.
 What is the relationship between the size of the energy gap between levels and the wavelength of the light
emitted? Bigger jumps produce (short / longer) wavelengths.
12. Add more energy levels.
 What happens to number of lines in the spectrum as # energy levels increases?
 Is it possible to make an atom that only has a single line in its emission spectrum? How?
 Is there any way to make an atom that has every line in its emission spectrum (in essence, a continuous
spectrum)? What would the configuration of its energy levels look like?
13. Choose Hydrogen as the Atom Type.
 As n increases, do the energy levels get closer together or farther apart?
 Are the lines in H's spectrum evenly spaced? If not, do they do the lines in the bright-line spectrum
converge (get closer) at higher wavelengths or lower wavelengths?
 Why do you think they are like this and not evenly spaced out?
 Is there any way to get them to be evenly spaced out? Choose Configurable and experiment. What do the
energy levels have to look like in order to produce a spectrum that has evenly spaced lines?
14. View Mercury’s spectrum under the Many Atoms tab.
 State two reasons why mercury’s spectrum is not identical to hydrogen's.
 Why does adding energy to atoms always produce a bright-line spectrum and not a continuous spectrum?
 When looking at an element’s spectrum, why do we see all four lines simultaneously?
Report: Turn in Conclusions sheet (answers to the bullet points q’s in full sentences). One per team of students.