Flame Test Lab

Flame Test Lab
PSI Chemistry
The normal orbit or energy level of an electron in an atom of an element is known as its
“ground state.” When atoms in the “ground state” are heated to high temperatures, some
electrons may absorb enough energy to allow them to “jump” to higher energy levels. The
element is then said to be in the “excited state.” This excited configuration is unstable, and
the electrons “fall” back to their normal positions of lower energy (ground state). As the
electrons return to their normal levels, the energy that was absorbed is emitted in the form of
electromagnetic energy. Some of this energy may be in the form of visible light. The color of
this light can be used as a means of identifying the elements involved. Such analysis is
known as a flame test.
To do a flame test on a metallic element, the metal is first dissolved in a solution and the
solution is then held in the hot, blue flame of a Bunsen burner.
As you may know metals do not dissolve easily in water, so
instead we will being using ionic compounds which contain
metals ions. Metal ions are atoms of metal that have lost one
or more electrons, such as Mg2+ which has 10 electrons or
Fe3+ which has 23 electrons. The loss of electrons gives metal
ions a net positive charge. In an ionic compound they are
attracted by Coulombic forces to non-metallic ions, such as Clwhich have a net negative charge. Ionic compounds are
commonly referred to as salts. Salts dissolve easily in water.
Once dissolved a wire loop can be used to pass the solution through a flame. Different
elements will produce different amounts of energy when the electrons return to their ground
state resulting in different wavelengths of light.
Atomic Origins
Flame Test Lab
1. Observe the flame color produced by various metals.
2. Determine the identity of unknown metallic ions.
Pre lab Exercise:
1. Why do we expect different metals to produce different color flames when burned?
2. The metal ions being tested are Na+, K+, Li+, Ba2+, Cu2+, Sr2+, and Ca2+. How many
electrons are in each ion?
3. Classify the following processes as physical or chemical changes:
a. Dissolving the ionic compounds in water
b. Flame testing the solutions
Bunsen burner
6 small beakers
6 small weighing dishes
nichrome wire with loop
HCl (3M)
Salt Solutions: NaCl, KCl, LiCl, BaCl2, CuCl2,
SrCl2, CaCl2
Unknown salt solution(s)
Procedure *Put on googles and aprons before proceeding*
1. Light the Burner and adjust it so it has a hot blue flame.
2. Clean the nichrome wire loop by alternately heating the wire in the burner flame and
dipping it in a solution of concentrated hydrochloric acid. Repeat until the flame
remains almost colorless when the wire is heated in the flame.
3. Dip the wire loop in the hydrochloric acid then into one of the salts so that a small
amount of salt crystals stay on the wire loop. Bring the loop to the edge of the blue
flame to produce the color and record in the data table.
4. Repeat with the remaining salts. Conclude by performing a flame test with an
unknown salt and note the color.
Atomic Origins
Flame Color
Analysis Questions
1. What is the identity of the metal in the unknown?
2. Estimate the wavelength for each of the tested metal ions. Calculate the approximate
energy being emitted by each.
3. Some commercially available fireplace logs burn with a red and/or green flame. On the
basis of your data, what elements could be responsible for these colored flames?
Atomic Structure
4. Aerial fireworks contain gunpowder and chemicals that produce colors. What elements
would you include to produce the following colors?
a. Crimson red
b. Yellow
Atomic Structure