Atomic Spectra continued
2
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7. Turn OFF the power supply. Record the following information for the emission spectrum of hydrogen: the number of
lines, their colors, and their approximate wavelengths.
8. Using colored pencils, sketch the atomic spectrum of hydrogen in appropriate wavelength boxes. Turn the power supply on
and off, as necessary, to complete the observations in steps 7 and 8.
9. Check to make sure the power supply is off, then remove the hydrogen spectrum tube and insert a mercury spectrum tube.
10. Observe and note the atomic emission spectrum of mercury.
11. Turn OFF the power supply. Record the following information for the emission spectrum of mercury: the number of lines,
their colors, and their approximate wavelengths.
12. Using colored pencils, sketch the atomic spectrum of mercury in appropriate wavelength boxes. Cycle the power supply on
and off, as necessary, to complete the observations in steps 11 and 12.
13. Repeat steps 9–12 for any other gas spectrum tubes that are available.
14. Using a spectroscope, observe the spectrum of visible light obtained from a fluorescent light. What kind of spectrum is
produced? If any bright lines are present, record the number of lines, their colors, and their approximate wavelengths.
15. (Optional) Using a spectroscope, observe the emission spectrum of other light sources, such as neon signs, street lights,
headlights, novelty lamps, etc. What kind of spectra are produced? If any bright lines are present, record the number of
lines, their colors, and their approximate wavelengths.
Disposal
None required. Carefully store all equipment for future use.
Connecting to the National Standards
This laboratory activity relates to the following National Science Education Standards (1996):
Unifying Concepts and Processes: Grades K–12
Evidence, models, and explanation
Constancy, change, and measurement
Content Standards: Grades 9–12
Content Standard A: Science as Inquiry
Content Standard B: Physical Science, structure of atoms, structure and properties of matter, interactions of energy
and matter
Content Standard G: History and Nature of Science, nature of scientific knowledge, historical perspectives
Tips
• Using a spectroscope is an interesting and fun activity for students. Many teachers are discouraged from doing an
“Atomic Spectra” lab because of the expense involved in purchasing power supplies. Many inexpensive alternatives to
spectrum tubes are readily available, however, and may be used. Inexpensive “neon” novelty lamps available at many party
stores and discount stores are excellent sources of bright line emission spectra of mercury (blue) and neon (red).
• Check with the physics teacher at your school for power supplies, spectrum tubes, and spectroscopes.
• The “Spectrum Analysis Chart” available from Flinn Scientific (Catalog No. AP8676) is a poster-size, full-color chart that
shows the bright line emission spectra of ten elements.
• Take advantage of Internet resources to locate full-color reference spectra for many different gases. The following Web
site (accessed January 2010) showed a wide selection of atomic spectra.
http://astro.u-strasbg.fr/~koppen/discharge
• The line emission spectrum of an element can be compared to the UPC code found on many packaged items. The UPC
code consists of a series of lines—the pattern of lines, not any individual line, is characteristic of the item in question.
• Show students the colors of light reflected from a CD to illustrate what a diffraction grating is and what it does.