Chemlab: Chemistry 6

Spectrum of the Hydrogen Atom


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Before Lab
Before coming to lab, complete the prelab portion of your write-up in your notebook. This includes the objective, reference, four prelab problems, procedure, and analysis flowchart or sample calculations. In your analysis flowchart or sample calculations, be sure to include how to perform the calculation of the wavelength of an observed emission line, the energies of the 3s and 3p orbitals of sodium, and Zeff for the 3s and 3p energy levels of sodium.

In Lab
Record your data and observations in your notebook as you perform the experiment. Note any changes made in the procedure written in your prelab. Your lab write-up should include the following data for each line of the hydrogen and sodium spectra:

rulings/mm of the grating
color of each emission line
meterstick a reading from observer 1 position
meterstick a reading from observer 2 position
b distance
slit position on meterstick a

For helium, neon, mercury, and the fluorescent light, include a quantitatively accurate sketch of the observed spectra, showing the scale on meterstick a. You will not calculate wavelengths of the observed lines.

During the lab period, calculate the wavelength of at least one emission line and check your results with the values found in prelab problem 3. Also calculate the energies of the sodium 3s and 3p orbitals and the Zeff of each orbital. You may wish to do these calculations while you are waiting to observe the spectra of different elements. Your TA will not sign your notebook until you have completed this minimum set of sample calculations correctly. If you are having trouble with the calculations, check your units, then ask your TA for help.

After Lab
For hydrogen and sodium, you will calculate the wavelength of the spectral lines observed. For each observed line, you will need to calculate and show the following in the results section:

distance a for observer 1
distance a for observer 2
average distance a
tan θ
sin θ
wavelength λ

These results can be shown in a table and a sample of each type of calculation should be included. For the sodium spectrum, include the same information as for the hydrogen spectrum and also a calculation of the energy of the 3s and 3p orbitals and the Zeff for each orbital.

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