Visible light is the most familiar example of electromagnetic radiation. Differences in the wavelengths of visible light are manifested as different colors, shown in the Color Spectrum below colors can be seen in the PDF document on-line.
Other examples of electromagnetic radiation include X-rays, ultraviolet light, infrared light, microwaves and radio waves. So, how does electromagnetic radiation relate to flame tests? Well, when an atom or ion absorbs energy, its electrons can make transitions from lower energy levels to higher energy levels. The energy absorbed could be in the form of heat as in flame tests , or electrical energy, or electromagnetic radiation. However, when electrons subsequently return from higher energy levels to lower energy levels, energy is released predominantly in the form of electromagnetic radiation.
The spacing between energy levels in an atom determines the sizes of the transitions that occur, and thus the energy and wavelengths of the collection of photons emitted:. If emitted photons are in the visible region of the spectrum, they may be perceived as lines of different colors note that photons outside the visible spectrum may also be emitted, but cannot be seen by eye.
For example, the line spectra shown below for the elements helium and carbon are clearly quite different. Unfortunately, techniques more sophisticated than those used in this lab are required to obtain such line spectra. To the naked eye, when an element is vaporized in a flame or an electrical discharge the emission spectrum will appear to be just one color.
For example, helium gas when excited by an electrical discharge emits light that appears an orange-peach color. This one color results from a combination of all lines of the emission spectrum, in proportion to their intensities. As many elements will still produce distinctive colors under such conditions, simple flame tests can be used to identify these elements. In fact, flame tests were used to identify elements long before the invention of modern techniques, such as emission spectroscopy.
This experiment will be performed as an instructor demonstration only. Your instructor will dip a looped wire into one of the solutions supplied, and then hold it in the Bunsen burner flame. Students will record the dominant flame color observed. The table below contains a list of appropriate colors to choose from.
Your instructor will then repeat this for the remaining five solutions, using a fresh looped wire each time. Analysis: For each metal cation tested, obtain the wavelength of light corresponding to the observed flame color from the table below. Note that the wavelengths supplied here are in nanometers. Related questions When does an iron rod become magnetic? Which force field can accelerate an electron, but never change its speed? Which force field can increase a moving electron's speed?
Which pole of a compass needle points to a south pole of a magnet? Why is electromagnetism useful? Why is electromagnetism so important? Why are electromagnets used in electric appliances? Why are electromagnets made of soft iron? How can I create electromagnetism? The further you reach from the center of the flame, the lower the temperature will be. The orange, yellow, and red colors in a flame do not relate only to color temperature. Gas excitations also play a major role in flame color.
One of the major constituents in a burning flame is soot, which has a complex and diverse composition of carbon compounds. The variety of these compounds creates a practically continuous range of possible quantum states to which electrons can be excited. The color of light emitted depends on the energy emitted by each electron returning to its original state. Within the flame, regions of particles with similar energy transitions will create a seemingly continuous band of color.
For example, the red region of the flame contains a high proportion of particles with a difference in quantum state energies that corresponds to the red range of the visible light spectrum.
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