The Hydrogen Spectrum
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The Hydrogen Spectrum. Mike Jones. Pisgah High School Chemistry. Canton, NC. Rev 020804. In this experiment you will measure the wavelengths of the lines in the visible portion of the hydrogen spectrum and compare them to the calculated values predicted by the Bohr Model.

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Pisgah High School Chemistry

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Pisgah high school chemistry

The Hydrogen Spectrum

Mike Jones

Pisgah High School Chemistry

Canton, NC

Rev 020804


Pisgah high school chemistry

In this experiment you will measure the wavelengths of the lines in the visible portion of the hydrogen spectrum and compare them to the calculated values predicted by the Bohr Model.


Pisgah high school chemistry

This is a spectroscope

We can use it to measure the wavelengths of the lines in atomic spectra.


Pisgah high school chemistry

A high voltage is applied to a narrow tube filled with hydrogen gas and light is produced.


Pisgah high school chemistry

Behind the eyepiece is a transmission diffraction grating which separates the light into its components.


Pisgah high school chemistry

The spectral lines produced by the the diffraction grating appear superimposed over the scale.


Pisgah high school chemistry

The light from the hydrogen discharge tube passes through a narrow slit.


Pisgah high school chemistry

The spectral lines appear superimposed over the scale so that their wavelengths can be determined.


Pisgah high school chemistry

The wavelength is the number times 10-7 meters.

Or the wavelength is the number times 100 nanometers.


Pisgah high school chemistry

Light from the spectrum tube coming through the slit

Measure the wavelength of each line in meters and nanometers.

2 3 4 5 6

Actual photograph of hydrogen spectrum. - M. Jones 2/5/04


Pisgah high school chemistry

Now you will predict the wavelength of light emitted as the electron moves from a higher energy level to a lower energy level.

You will be given the energy level the electron comes from, and the energy level the electron goes to.


Pisgah high school chemistry

Use Bohr’s equation to predict the energy of each allowed state.

n is the principal quantum number and has values of 1, 2, 3 … 7


Pisgah high school chemistry

Rh is called the Rydberg Constant,

Rh has a value of 2.18 x 10-18 J.


Pisgah high school chemistry

Next, find the difference between the two allowed energy states.

DE = E final – E initial

Then, compute the wavelength.


Pisgah high school chemistry

Complete a table like the one below.


Pisgah high school chemistry

You will now combine your results with the results of other students to compile a list of all of the possible transitions from a higher energy level to a lower energy level, which give off light.

A table like the following one will be on the board.


Pisgah high school chemistry

These transitions do not result in an emission.

Enter the wavelengths in nanometers here.

…these lower levels


Pisgah high school chemistry

Finally, compare the wavelengths you measured to the wavelengths predicted by the Bohr model.

How do they compare? Were all of these lines visible?

In what parts of the electromagnetic spectrum do they appear?


Pisgah high school chemistry

Do the results of your experiment support the Bohr Model?

Why or why not?

What additional experiments could you do in order to further test the model?


Pisgah high school chemistry

Send questions, comments, and suggestions to:

Mike Jones

Pisgah High School

1 Black Bear Drive

Canton, NC 28716

828-646-3463

[email protected]


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