DE LA SALLE HEALTH SCIENCES INSTITUTE
CITY OF DASMARIÑAS
EXPERIMENT NO. 5
FLAME COLOR OF METALS
1. To observe the flame colors emitted by excited metal atoms
2. To explain the flame colors in terms of electronic transitions in atoms
The current model of an atom includes a nucleus, consisting of protons and neutrons, surrounded by electrons. According to experiments on atomic absorption and emission spectra, the energy of electrons is quantized. It means that each electron in an atom has a definite energy.
When an atom absorbs energy from a flame or electric discharge, it absorbs just enough energy to excite its electrons from a lower ...view middle of the document...
Thus, excited sodium atom produces yellow color while excited barium atom produces a green color.
Platinum or nichrome wire 10 ml 37 % Hydrochloric acid, HCl
Alcohol lamp 20 ml distilled water
Watch glass Calcium chloride crystals, CaCl2
Stirring rod Potassium chloride, KCl
Medicine dropper Sodium chloride, NaCl
Copper (II) chloride, CuCl2
Barium chloride, BaCl2
1. Dip the end of a platinum or nichrome wire into 37% HCl.
2. Heat the wire in the flame’s hottest region until there is no visible color.
3. Repeat this cleaning procedure as necessary.
4. On a watch glass, add few crystals of CaCl2 to 2 to 3 drops of distilled water.
5. Stir to dissolve.
6. Dip the clean wire into salt solution and return it to the hottest part.
7. Note the flame color.
8. Repeat the process using other salts.
Table 1. Correlation between wavelength and color
|Wavelength (nm) |Color |
|380-435 |Violet |
|435-480 |Blue |
|480-490 |Green-blue |
|490-500 |Blue-green |
|500-560 |Green |
|560-580 |Yellow-green |
|580-595 |Yellow |
|595-650 |Orange |
|650-750 |Red |
Figueroa L.V., and Samonte J.L. General Chemistry Laboratory Manual. 3rd edition.
C & E Publishing, Inc. 2007
Atkins, P.W. and J.A. Beran. General Chemistry. 2nd Edition. New York: Scientific American Books, 1989
Prepared by: Noted by:
MR. RICARDO G. CAUSAREN MRS. MINERVA R. BASILIO, MAEd-Chem
Subject Coordinator Coordinator, Natural Science