Ashley Schaendorf
4th Hour
Atomic Spectra and Atomic Structure Lab
Introduction
A simple mechanic has an everyday job of fixing problems with peoples cars.
They have to determine an unknown. Many people bring their cars to them so that they
can figure out what the problem is. They do this by simply running tests and using
previous knowledge to determine the “unknown”. Well, this is similar to chemistry. In
chemistry wavelengths of emission lines can be determined. A wavelength is the
distance between two points, in which a wave repeats. Each wavelength is assigned a
certain color, also. Not only are there wavelengths, but there are also line spectrums.
These are a pattern of lines that can be seen through a spectrometer, it shows what
wavelengths are being emitted. However, by using a spectrometer, there can be a percent
error. They can be inaccurate and difficult to read. This is where the percent error comes
in. This will show how close the experimental value is to the actual, true value.
Therefore, if the wavelengths of emission lines are determined, then the unknowns may
be determined.
Materials and Methods
To begin with, a Bunsen burner and spectroscopes were obtained. The Bunsen
burner was lit, and a spray bottle containing calcium was obtained. The calcium was
sprayed on the flame numerous times. Observations were taken through the spectroscope
and recorded. Next, a spray bottle containing sodium was obtained and the sodium was
sprayed on the flame. Observations were taken through the spectroscope and recorded.
Barium was next obtained and sprayed on the flame. Observations were taken through
the spectroscope and recorded. Lithium was obtained next and sprayed on the flame.
Observations were taken through the spectroscope and recorded. Lastly, potassium was
obtained and sprayed on the flame. Observations were taken through the spectroscope
and recorded. The lab station was then cleaned up and the Bunsen burner was left at the
station. The next day, a spectroscope was obtained. The lab was then restarted and
completed as a class. Lithium, strontium, potassium, sodium, calcium, barium, and the
two unknowns were all placed in that order on top of a lab station. Ethanol was added to
the lithium and lit on fire. Observations were viewed through the spectroscope and
shouted out and were wrote on the board. Ethanol was added to strontium next and lit on
fire. Observations were viewed through the spectroscope and shouted out and were wrote
on the board. The same process was completed for potassium, sodium, calcium, barium,
and the two unknowns. Lastly, ethanol was lit on fire alone, and observations were
viewed through the spectroscope and shouted out and were wrote on the board. The same
task was completed using the light bulb that was being used for background light. The
observations were copied down. However, the hydrogen portion was not completed
correctly and the observations were copied down from another group. The lab was then
completed.
Ashley Schaendorf
4th Hour
Results
Table 1: Wavelength Related to Energy Transitions
Level 6 to 2
level 5 to 2
level 4 to 2
level 3 to 2
410.76 nm
434.67 nm
486.83 nm
657.22 nm
Level 6 to 2 Calculation:
1 / λ = R/H/C(1/(nf)2 – 1/(ni)2)
1 / λ = R/H/C(1/(2) 2 – 1/(6) 2)
1 / λ = 2434500.866
1 / λ = 2434500.866 -1
1 / λ = 4.1076 x 10-7 m x 109
1 / λ = 410.76 nm
Observed
Wavelength
430 nm
450 nm
500 nm
630 nm
Table 2: Hydrogen
True
Observed Color Wavelength
Purple
407 nm
Blue
430 nm
Teal
485 nm
Red
655 nm
Observed
wavelength
450 nm
510 nm
560 nm
650 nm
710 nm
Table 3: Lithium
True
Observed color wavelength
Purple
459 nm
Teal
496 nm
Light Green
N/A
Orange
611 nm
Red
671 nm
Observed
wavelength
450 nm
500 nm
570 nm
610 nm
700 nm
Table 3: Strontium
True
Observed color wavelength
Purple
405 nm
Teal
448 nm
Green
502 nm
Orange
(yellow) 587 nm
Red
668 nm
% error
5.65%
4.65%
3.09%
-3.82%
% error
-1.96%
2.82%
N/A
6.38%
5.81%
% error
11.10%
11.60%
13.50%
3.92%
4.79%
Ashley Schaendorf
4th Hour
Table 4: Potassium
Observed
wavelength
440 nm
500 nm
560 nm
600 nm
650 nm
Observed color
Purple
Teal
Green
Orange
Red
True
wavelength
435 nm
497 nm
545 nm
(yellow) 590 nm
no red
Observed
wavelength
450 nm
500 nm
560 nm
640 nm
Table 5: Sodium
True
Observed color wavelength
Purple
(blue) 455 nm
Teal
475 nm
Green
565 nm
Orange
630 nm
Observed
wavelength
450 nm
510 nm
560 nm
600 nm
610 nm
Table 6: Barium
True
Observed color wavelength
Purple
412 nm
Teal
490 nm
Green
555 nm
Yellow
575-585 nm
Orange
605-610 nm
Observed
wavelength
440 nm
500 nm
560 nm
600 nm
650 nm
Table 7: Calcium
True
Observed color wavelength
Purple
445 nm
Teal
485 nm
Green
no green
Yellow
no yellow
Orange
615 nm
Table 8: Light
Observed
wavelength
430 nm
450 nm
500 nm
560 nm
610 nm
640 nm
Observed color
Purple
Blue
Teal
Green
Yellow
Orange
% error
1.15%
0.60%
2.75%
1.69%
N/A
% error
-1.10%
5.26%
-0.89%
1.59%
% error
9.22%
4.08%
0.90%
2.56%
0.00%
% error
-1.12%
3.09%
N/A
N/A
5.69%
Ashley Schaendorf
4th Hour
Table 9: Ethanol
Observed
wavelength
450 nm
500 nm
560 nm
640 nm
Observed color
Purple
Teal
Green
Orange
The true wavelengths were either found in the General Chemistry text book or at
http://astro.u-strasbg.fr/~koppen/discharge/
Unknowns:
Unknown 1 – barium and lithium
Unknown 2 – barium and sodium
Conclusion
At first, this lab was not completed correctly. So, it was then completed as a
whole class. Due to this, the lab does not entirely make sense. Many of the students
could not read out of the spectrometer, so the readings came from only a couple students.
The spectroscopes were also hard to read and somewhat inaccurate. The lighting in the
room was inadequate and didn’t light up the spectrum enough to make it readable, unless
one was close enough to the flame. The unknowns were determined using the line
spectrums and comparing what spectrums were in the unknowns and as well in the other
solutions. Looking at the flame would not have been enough, due to the fact that some of
the flames looked very similar. All of the solutions were burned in ethanol, also. This
could have had an impact on the line spectrum. Many of the line spectrum recordings
were the same throughout the lab, such as the 450nm, 500nm, and the 560 nm. This was
proven because when ethanol was burned by itself, it had those same exact readings.
Possibly, if the lab was completed in individual groups, but each group had enough
lighting, the results could have been more accurate. So, as it is visible, figuring out the
proper unknown is very important. Not only in chemistry, but it is also important in the
everyday world. Teachers often have to figure out an unknown, which is most of the
time a no name paper. If the teacher does not find the correct student, the points for the
paper could go to somebody else.