FLAME TEST FOR METALS
EXPERIMENT 5
1
PURPOSE
1. To observe and identify metallic ions using flame tests.
2. To determine how the energy of light emitted from the excited state of an atom is related to the
electronic structure of that atom.
DEFINITIONS
Orbital, electron energy level, ground state, emission spectrum of an atom.
BACKGROUND
Have you ever wondered why a candle flame is yellow? The characteristic yellow of a candle flame
comes from the glow of burning carbon compounds. When elements, such as carbon, are heated to high
temperatures, some of their electrons are excited to higher energy levels. When these excited electrons
fall back to lower energy levels, they release excess energy in packages of light called photons, or light
quanta. The color of the emitted light depends on its energy. Blue light is more energetic than red light,
for example. When heated, each element emits a characteristic pattern of light energies, which is useful
for identifying the element. The characteristic colors of light produced when substances are heated in the
flame of a gas burner are the basis of flame tests for several elements. In this experiment, you will
perform the flame tests used to identify several metallic elements.
MATERIALS
platinum wire or nichrome wire
solution of potassium nitrate, KNO3
solution of calcium nitrate, Ca(NO3)2
solution of lithium nitrate, LiNO3
solution of sodium nitrate, NaNO3
solution of barium nitrate, Ba(NO3)2
solution of copper(II) nitrate, Cu(NO3)2
solution of strontium nitrate, Sr(NO3)2
SAFETY
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The solutions used in this lab contain harmful materials. Avoid skin contact.
Wear your safety goggles.
Do not taste any of the substances or touch them with your hands (duh!).
Do not at any time touch the end of the wire loop used in the flame tests. This wire gets extremely hot
and can cause severe burns.
PROCEDURE
As you perform the experiment, record your observations in Data Table 1.
1. There is a separate wire loop for each solution of metal ions that you will test. Do not crosscontaminate the wire loops.
2. Dip the wire loop into the test tube containing a solution of one of the metal salts. Heat the sample in
the burner flame. Record the color of the flame when the wire loop first enters the flame. Be creative
when describing the colors, for example use nail polish or Crayola crayon names. Test the remaining
samples in the same way, each with its own wire loop. Record your observations.
3. Perform a flame test on the unknown salt solution. The unknown is the same as one of the metal ions
you already tested. Record your observations.
FLAME TEST FOR METALS
EXPERIMENT 5
2
ANALYSIS
1. State the most important safety concern in this lab and the required precaution you took.
2. Describe the process taking place within an atom that leads to the emission of light.
3. What is the relationship between the energy of the emitted light (photon) and the electron energy
levels in an atom?
4. List the elements that produced the most easily identified colors.
5. Which elements are least easily identified? Explain.
6. Based on the color of light you observed, what is the identity of the unknown element?
7. Would flame tests be useful for detecting metal ions present in a mixture of metal ions? Explain.
8. The energy of colored light increases in the order red, yellow, green, blue, violet. List the metallic
elements used in the flame tests in increasing order of the energy of the light emitted.
9. Honors: What was the most probable source of error that would lead to incorrect observations?
OBSERVATIONS
DATA TABLE 1: FLAME TEST
Ion
sodium, Na+
potassium, K+
calcium, Ca2+
barium, Ba2+
strontium, Sr2+
lithium, Li+
copper, Cu2+
unknown
Flame Color