Atomic Spectroscopy

Topics: Light, Electromagnetic radiation, Photon Pages: 3 (1343 words) Published: November 3, 2014

CH 204
DateExperiment 3: Atomic Spectroscopy
The purpose of the atomic spectroscopy lab experiment was to investigate the relationship between visible light, which is the visibly observable range of electromagnetic radiation and the change in energy levels of an element. The line spectrum that was seen in the spectroscope was the evidence of excited atoms emitting electrons and radiating a spectrum of light as it moved from a higher energy state back down to a lower energy level. Using a spectrometer with diffraction grating, a hydrogen lamp was observed and emission wavelengths compared with the known wavelength values. Flames from ignited sodium chloride were also observed and wavelengths calculated. To calculate the observed values of hydrogen and sodium, a calibration curve was made from the wavelengths observed from a mercury lamp. The wavelengths of hydrogen and sodium were determined by calculations made with the best fit line equation from the mercury in eq 1. y=mx+b (1)

The energy of each line in the hydrogen spectrum was calculated using Einstein’s formula for calculating the energy of photons¹. Einstein derived this formula after he expanded Planck’s quantum theory combining both Planck’s constant multiplied times the frequency of light as seen in eq 2. E=hv=hc/λ (2)

In equation 2, E is the energy measured, h is Planck’s constant of 6.63 x 10-34 J∙s, and v is the frequency of light. In the second formula offered in eq 2, c is the constant for the velocity of light which is 3.0 x 108 m/s multiplied by h, then divided by the wavelength. Use of the second formula was used in this experiment after the experimental wavelengths were calculated. The accuracy of the wavelengths measured was determined by calculating the percent relative error (PRE), using values listed in our lab manual for hydrogen. ² Procedure

A spectroscope was constructed according to instructions in the course manual.² A sighting hole with a...

References: Brown, T.L.; LeMay, H.E., Jr.; Bursten, B.E.; Murphy, C.J.; Woodward, P.M.; Chemistry: The Central Science, 12th Edition; Pearson; Glenview, IL, 2012; p. 213-214
Atomic Spectroscopy; General Chemistry Experiments: A Manual for Chemistry 204, 205, and 206, Department of Chemistry, Southern Oregon University: Ashland, OR, 2014; pp. 28-32
Atomic Spectra at RudgersU. (accessed Oct 22, 2014.)
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