LAB 5 – ATOMIC SPECTRA
Before lab, these questions must be answered on the pre lab questions page in
your notebook. This page should come after page 1.
1. Name the colors of visible light, beginning with that of lowest energy.
2. Distinguish between absorption and emission of energy.
3. A system proposed by the U.S. Navy for underwater submarine
communication, called ELF (for “extremely low frequency”), operates with a
frequency of 76 Hz. What is the wavelength of this radiation in meters? In
miles? (1 mile = 1.61 km)
4. What is the energy in joules of the frequency given in question 3?
5. Red and green light has wavelengths of 650 nm and 490 nm, respectively.
Which light has the higher frequency? Which has the higher energy?
6. Mg emits radiation at 285 nm. Could a spectroscope be used to detect this
emission?
7. If boron emits radiation at 518 nm, what color will boron impart to a flame?
Purpose
To gain some understanding of the relationship between line spectra and
atomic structure
Background
Lots to do for this page!!!!
Procedure
You will obtain the emission spectra of the ions of the elements in solution that are
prepared for you. You will use a Bunsen burner as an excitation source and observe
the color imparted to the flame by these ions. Make an appropriate table.
You will be using solutions that contain the following ions: Ba, Ca, Cu, K, Li, Na, and
Sr.
1. Practice using the spectroscope. I will demonstrate its use. Observe the
fluorescent light in the room. You should see wavelengths of light in the
purple, blue, green (546 nm), yellow, and red regions. Become familiar with
the scale.
2. The solutions of metal ions will be poured and labeled for you.
3. Put distilled water into the small beaker.
4. Clean your wire-loop with HCl (in the small test tube) and then distilled
water and heat the wire-loop in the hottest part of the flame until it imparts
no color to the flame. Do this after testing with each solution.
5. Dip the wire loop into the first solution and place it into the flame. Note the
color imparted to the flame and record it in the table in your notebook.
6. Follow the above procedure for each solution.
7. Using the spectroscope, observe the line spectra for hydrogen and three
other elements. Make sure you have an appropriate table in your notebook.
Record the wavelengths of as many lines as possible in your table.