Santa Monica College
Chemistry 11
Name:
Date:
Lab Partner:
Lab Section:
Lab Report: Atomic Emission Spectra
Part A: Construction and Calibration of the Spectroscope
Experimental Data
•
On the figure below, sketch in the observed line spectrum of mercury.
•
Record the following for the 4 brightest lines observed:
Line Color
Spectral Line Position (mm)
Actual Wavelength (nm)
Data Analysis
1) Using Excel, plot “Wavelength (Y) versus Spectral Line Position (X)”. Attach this graph to
your lab report. Add a trendline to your data and obtain the equation for this best-fit line.
Record this calibration equation below.
Calibration Equation:
2) Would your calibration equation work for another person’s spectroscope? Why or why not?
Atomic Emission Spectra
-1-
Santa Monica College
Chemistry 11
Part B: Spectrum of a Single Electron Element – Hydrogen
Experimental Data
•
Record the following for the brightest lines observed (3 or 4):
Line Color
Spectral Line Position (mm)
Wavelength (nm)
from Calibration Equation
Data Analysis
1) For the first four electronic transitions in the Balmer Series, calculate:
-- the change in energy of the electron, ∆E
-- the predicted energy of the emitted photon, Ephoton
-- the predicted wavelength of the emitted photon, λphoton
Electronic Transition
∆E (J)
Ephoton (J)
λphoton (nm)
n3 → n2
n4 → n2
n5 → n2
n6 → n2
Clearly show the following calculations for the n3 → n2 transition.
-- the change in energy of the electron, ∆E
-- the predicted wavelength of the emitted photon, λphoton
Atomic Emission Spectra
-2-
Santa Monica College
Chemistry 11
2) Based on your theoretical calculations, match the electronic transitions in the Balmer Series
to the spectral lines you observed. Then calculate the percent error between your
experimentally determined and calculated wavelengths.
Spectral Line
Color Observed
Experimental
Wavelength (nm)
Calculated
Wavelength (nm)
Electronic
Transition
Percent Error
Below, clearly show your percent error calculation for the the the n3 → n2 transition.
3) It is not possible to observe the n7 → n2 transition in the Balmer Series. Why is that?
Part C: Spectrum of a Polyelectronic Element
Experimental Data
•
Element name:
•
Record the following for up to 6 of the brightest lines observed:
Line Color
Atomic Emission Spectra
Spectral Line Position (mm)
Wavelength (nm)
from Calibration Equation
-3-
Santa Monica College
Chemistry 11
Data Analysis
1) Go to the website: http://physics.nist.gov/PhysRefData/Handbook/element_name.htm
Select the name of the element you chose, then click on the box labeled “Strong Lines”. Scan the
wavelength column for the wavelengths you measured to see if you can find any close matches.
Note the following:
•
The tabulated wavelengths are given in units of Angstroms (1 A = 10-10 m). The wavelengths
you have measured in lab are in nm (1 nm = 10-9 m). Thus, you must convert the numbers in
the NIST table to nanometers before recording them below (divide by 10).
•
Each element actually emits hundreds of wavelengths of light, but only a few are emitted with
enough intensity (brightness) for our eyes to see them. The tabulated wavelengths include
those that we cannot see with the naked eye, so you must scan down the “Intensity” column
in the table of wavelengths. Look for those lines that have very high values for intensity
compared to the rest – these are the ones you are likely to have seen in lab. Note that this
means the wavelengths may not match perfectly.
Record the tabulated (actual) wavelength for the intense line nearest to each wavelength you
observed. Then calculate the percent error for each of your measured wavelengths.
Spectral Line Color
Observed
Experimental
Wavelength (nm)
Actual Wavelength
(nm) from website
Percent Error
2) Why can’t the Bohr Theory be used to calculate the predicted wavelengths of emitted
photons in the line spectra of polyelectronic elements?
Atomic Emission Spectra
-4-