1. Interaction between atoms and light.
Spectroscopy
Interaction between atoms and light.

2. Light Light is the key to understanding the modern atom.
Source: Wikimedia Commons
Light is the key to understanding the modern atom.
Has both wave and particle properties depending on how you measure it.
A packet of light is called a photon.

3. All electromagnetic radiation is light.
Source: North Carolina End-of-Course Chemistry Reference Table
All electromagnetic radiation is light.

4. Wavelength
Wavelength – λ (lambda) – the distance between two equivalent points on a wave.
Measured in length units, (m, nm, pm, etc.)
Source: library.thinkquest.org, Used by permission

5. Characteristics of Light
Frequency – ν (nu) – the number of times a particular point on a wave passes by an observer in one second.
Measured in Hertz, Hz = 1/s
Source: Wikimedia Commons

6. Relationship Between Frequency and Wavelength
Source: Wikimedia Commons
Wavelength and Frequency are Inversely Related
As one goes up the other goes down.
c = λν
c = speed of light = x 108 m/s

7. Characteristics of Light
There are a wide range of frequencies and wavelengths of light.

8. Characteristics of Light
One photon of light can transfer only a specific amount of energy
The energy of one photon, E = hν
E = energy of one photon
h = Planck’s constant, x J•s
v = frequency
Energy is proportional to frequency

9. Which light can do the most damage to you?
Source: North Carolina End-of-Course Chemistry Reference Table
Which light can do the most damage to you?
Short wavelength and high frequency has the highest energy

10. Light Wavelength and Frequency are inversely related.
Frequency and Energy are directly related.
Wavelength and Energy are inversely related.

11. Practice Problems
The newly developing LTE cell networks are in the 700MHz band. Verizon’s uplink band starts at 777MHz. What is the wavelength of a photon of this light?
What is the energy of a photon transmitted at 777MHz?

12. Atomic Spectra Emission Spectrum Flame Tests Discharge Tubes
Spectrum of light emitted by a substance when energy is added.
Flame Tests
Discharge Tubes

14. Atom Emission Spectra

15. Atom Emission Spectra

16. Simple Initial Model Hydrogen Atom Only one electron
Therefore, quantum mechanical calculations simplify tremendously.
All subshells are degenerate with each other in the same shell.
We can just worry about transitions from one shell to another shell with out caring about what subshell it ends up in.

18. Specific Energy Levels n = 1,2,3,4, etc.
Source: North Carolina End-of-Course Chemistry Reference Table
Specific Energy Levels
n = 1,2,3,4, etc.
Transition from “excited” state to “ground” state and the light produced by the transition.

19. Multi-Electron Atoms Subshells are not all the same energy.
Determining the transitions becomes much harder.

20. Emission Spectrum 670nm = 1s22p1 to 1s22s1 610nm = 1s23d1 to 1s22p1
Excited state to ground state
Strongest line and gives lithium flame test its color.
610nm = 1s23d1 to 1s22p1
Excited state to lower excited state
497nm = 1s24s1 to 1s22p1
460nm = 1s24d1 to 1s22p1

21. Practice
What is the energy of a photon emitted from a hydrogen atom when an electron jumps from n = 3 to n = 1?

22. Test Review Problem
In graphite, carbon atoms are about 142pm apart. This distance could be resolved by a system that emitted a wavelength of light roughly half of that distance. What is the frequency and energy of this light?

23. Test Review Problem
Chlorofluorocarbons, or CFC’s, have been banned from production in the US since When they are released into the air, they may migrate into the upper atmosphere. In the upper atmosphere, the carbon-chlorine bonds can be broken by a photon of light with energy of 5.45x10-19 J. The free chlorine atom can go on to cause the decomposition of multiple ozone molecules in a catalytic process (and therefore why they are banned). What is the wavelength of light that can cause the bond to break?

24. Old cordless phones used a 700
Old cordless phones used a 700.0MHz band for communication with the base station. What is the wavelength and energy of a photon of this light?