Electrons and Quantum Mechanics - Oakland Schools

Electrons & Quantum Mechanics
Activity #3 - Flame Test Lab
Questions to be investigated
How do we identify metals?
Objectives
Students will observe and identify elements based on the color produced in a flame test.
Teacher Notes
Background information
• Remind students to wear safety goggles and follow all lab rules.
• To avoid having students walk around during the lab, put a set of
solutions in small beakers or vials labeled at each lab table. There
should be two lab groups per table and they should share the
solutions. A student helper would distribute the unknowns, again to
keep students from leaving their lab tables.
• In order for students to obtain maximum results, have the lights in the
classroom dim. This is particularly helpful if the students are using a
spectroscope or diffraction grating.
By heating the elements, the electrons in the atom become excited. When the electrons
fall back to their ground state, they give off photons of light at characteristic energies.
If the amount or abundance of an element present is altered, it is possible to change
the intensity of the lines, (their brightness), because more photons would be produced.
But it is not possible to change their characteristic colors - no matter how much or how
little was present, the pattern of lines would be the same.
Gather materials. Platinum or nichrome wire may be used. Compounds with
chloride as the anion may be substituted for the nitrates. For example, sodium
chloride can be used instead of sodium nitrate. This lab can also be done using 6M
HCl as the cleaning agent instead of the 1M. The student handout uses 1M for
safety reasons. The solutions used can be 0.5 M or stronger.
Discussion and wrap up
Discuss the applications of flame tests. Ask students how else they might be useful.
Discuss the limitations of flame tests. A test viewed only with the naked eye is limited
by individual color interpretations and by ambiguities. For example, rubidium and
cesium produce the same color as potassium. Blue cobalt glass can be used to filter out
the light for a better color contrast.
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