Atomic Spectra
Light, Energy, and Electron Structure

Introduction: Sunlight passing through a prism produces a rainbow of colors – the visible spectrum. The separation of white light into its component colors occurs when light waves of different wavelengths are bent by different amounts. When a pure atomic gas such as hydrogen or helium is subjected to a high-voltage electrical discharge, light is produced and the gas glows. When this light is passed through a diffraction grating, however, the spectrum it produces is different. Instead of giving the familiar rainbow of colors, the light emitted by the gas gives a series of bright, colored lines. The series of bright lines is called an atomic emission spectrum and is unique to each element.

Concepts: Atomic emission spectrum Electron energy levels Quantization of energy Electron transitions Background: Hmmm… You’re on your own for this one. Use your textbook and/or internet resources to develop a background section in your lab.
Include the following information in your background:
• Definitions of each of the concepts listed above.
• Scientists and the major contributions they made to these concepts.
• Terms such as “ground state”, “excited state”, “electromagnetic radiation”, and “photon”.
• Niels Bohr’s formula for the relationship between the energy of light and its wavelength.
• What aspect of Bohr’s original model of electron structure is still included in the currently accepted theory of electron structure?
• What aspect of Bohr’s original model of electron structure is no longer considered valid in the currently accepted theory of electron structure?

Materials: Colored pencils Diffraction grating or spectroscope Gas discharge tubes (TBA) Power supply Procedure:

1. Using the spectroscope or a diffraction grating, observe the continuous “rainbow” spectrum from an incandescent light bulb.

2. Observe the colors of light in the visible spectrum and the