Experiment B: Atoms and Line Spectra Flashcards
What are the the three objectives
Use visible light spectroscopy:
- record the atomic line spectra for 3 elements using a series of gas discharge tubes
- do flame tests on a series of metal salts
- record the absorption line spectra of two diff colour smarties
Gaseous discharge tubes emit light of a ______ spectrum
Atoms of the gas are excited by passage of an ____ _____
Discontinuous electric current
When excited atoms return to a lower state, a ___ is emitted
Photon
Atoms of the gas are excited by passage of an electric current from an _____ at one end of the tube to an ______ at the other end
Electrode
How are wavelength and energy determined
By the energy levels for that element
What are the two common applications of light emission by elements
Flame test and fireworks
What is a flame test used for and why
To identify the presence of elements
A bit of the solid is atomized and excited in a flame, this is identified by resultant colour of flame
What variable represents nuclear charge
Z
Formula for speed, wavelength, and frequency
c= lambda(freq)
What is energy of a photon equal to (2 equations)
E = hv = hc
List the colours in INCREASING wavelength
violet, blue, green, yellow, orange, red
What are the two formula for energy with “n”
E = (-Z^2(Rh))/n^2
triangle E =( -Z^2(Rh))(1/nf^2 - 1/ni^2)
What is the Lyman series
ni —-> nf = 1
What is the balmer series
ni —-> nf=2
What is the Paschen series
ni —-> nf= 3
What does the spectrometer measure
And how (3)
The absorption spectra of aqueous solutions of the dyes coating the smarties
1) Light from source is split into a narrow range of wavelengths and passed through the sample
2) some of that might be absorbed
3) spectrometer will obtain values of “A” as wavelength changes
What is the graph of that we printed out
“A” vs. Wavelength of incident light
= spectrum
What is the function “A” on the spectrometer
Abs what is it related to
Absorbance
Directly related to the amount of absorption
What does a larger “A” value mean on the spectrometer
More of the incident light is absorbed
Experiments procedure for the discharge tubes
To observe the line spectra: set square hole of spectroscope at the middle of, almost touching the discharge tube
If you place it too far away you’ll see lines for lights in the room
Experimental procedure for flame tests (2)
1) dip tip of Pt wire into concentrated H and heat tip of flame, repeat
2) put a solid crystal of LiCl on wire and heat tip on flame
What are the compartments inside the spectrometer called
(2)
Big compartment = sample compartment
Small containers inside = cuvette
For the discharge tubes, the lines in the spectroscope that don’t come close to matching calculated lines are due to what?
Human error
What does the shortest wavelength correspond to for all the series
n = inf to n=2
