1. Electron Emission Spectra

2. Overview Types of waves Parts of a wave
Relating wavelength and frequency
Electromagnetic spectrum
Atomic spectrum
Calculate the wavelength of light emitted
Relating it all to Heisenberg’s Uncertainty Principle

3. Parts of a wave
In Physical Science and Earth Science you (should have) learned about two types of waves:
Longitudinal a.k.a. compression waves
Sound waves and P waves from earthquakes
Transmit energy as vibrations that move matter
Cannot travel in a vacuum because they need to bounce off of atoms
Transverse
Light and water waves as well as S-waves from earthquakes
Transmit energy in small particles of energy called photons
The various wavelengths make up the electromagnetic spectrum

4. Parts of a Transverse Wave
Increased amplitude
Increased wavelength, decreased frequency

5. Frequency and Wavelength Relationship
Frequency is the number of waves (or cycles) that pass a particular location in 1 second.
The SI unit is Hertz (or s-1)
The symbol is the greek letter gnu (ν)
Wavelength is the length of a wave
The SI unit for wavelength is meters (m)
The symbol is the greek letter lambda (λ)
Frequency and wavelength are inversely proportional
As frequency increases, the wavelength decreases
As frequency decreases, the wavelength increases
They are related by the following equation:
c=λν
Where c is the speed of light (2.998 x 108 m/s)
You will be expected to use this equation to determine the wavelength if given the frequency of light and vice versa. (pg 140)

6. The Electromagnetic Spectrum
Light, as we know can have various wavelengths and frequencies. These fit an entire spectrum called the electromagnetic spectrum
As you move to the right, the waves become increasingly dangerous
Find the following:
Waves with the longest λ
Waves with the shortest λ
Waves with the highest ν
Waves with the lowest ν
Color of light with the highest ν
Color of light with the lowest ν
Color of light with the longest λ
Color of light with the shortest λ
What is the speed of red light?
What is the speed of blue light?

7. Now using your reference tables, answer the following questions
What is the frequency of green light?
What is the wavelength of blue light?
What is range of frequencies people can see?
What is the range of wavelengths in the visible spectrum?
What is a wavelength for the infrared heat lamp used to keep your food warm at McDonald’s? Is this more or less dangerous than visible light?

8. Atomic Emissions We’ve learned: What we’ve not touched on yet is:
about the electrons being found in various levels in an atom.
electrons prefer to stay in electron shell that requires the lowest energy before filling those that need higher energies to be occupied (i.e. we fill the s-shell before the p-shell, because it requires less energy)
What we’ve not touched on yet is:
If we give an electron extra energy, it becomes excited and jumps.
If the electron is given enough energy it can jump to a different electron shell.
jump from s to p, d, or f
Jump from p to d or f
After a while, the electron falls back to a lower energy shell.
Because it’s dropping back to a lower shell, it must give off energy
The energy is released as light
The photon of light varies depending on the amount of energy released.
The equation E=hv can be used to determine the frequency of light emitted, (where h = Plank’s constant) but we will not use this equation this year.
If you combine the various colors emitted from a single element, you create an emission spectrum

9. Apply it to the Bohr Model
This works great for Hydrogen!
If we give an electron extra energy, it becomes excited and jumps.
If the electron is given enough energy it can jump to a different electron shell.
jump from s to p, d, or f
Jump from p to d or f
After a while, the electron falls back to a lower energy shell.
Because it’s dropping back to a lower shell, it must give off energy
The energy is released as light
The photon of light varies depending on the amount of energy released.
If you combine the various colors emitted from a single element, you create an emission spectrum

10. The Bohr model worked great for Hydrogen!
However, the emission spectra for other elements did not fit with the idea that there were only certain levels for the electrons to move to/from.
The quantum mechanical model was developed to support the complex atomic emission spectra found for other elements
This required there to be s, p, d, and f shells in each level

11. Lyman, Balmer, and Paschen Series
emits ultraviolet light
Fall to the n = 1 energy level
Balmer
emits visible light
Fall to the n = 2 energy level
Paschen
emits infrared light
Fall to the n = 3 energy level

12. The point…. The quantum mechanical model was developed.
Light travels as a wave in a ball of energy we call a photon
The electrons can get excited and give off their energy as they fall back to a lower energy shell
This relates back to Heizenberg’s Uncertainty Principle