Light and Planck's Constant

Notes for Page 29.

Review: (all Review Points taken from Page 17)
1) Energy of electrons increases as you move away from the nucleus.
2) You cannot pinpoint the exact location of an electron - only the general area (Heisenburg Uncertainty Principle - loosely)
3) Bohr put electrons in orbitals.

Waves:

Frequency is inversly proportional to wavelength

- As frequency increases, wavelength decreases (gets shorter)
- As frequency decreases, wavelength increases (gets longer)

The formula for the relationship between frequency and wavelength is:

Why do I care about waves?

 1) Light travels in waves

 2) Electrons are made of light

Light

- Travels in waves

- Very fast

- Electromagnetic Spectrum



How does this apply to Chemistry?

- Electrons are photons of light

- Atoms have an emission spectrum!

   * called the Atomic Emission Spectrum

   * Unique to each element

      (this is how they determine what stars are made of)

   * Seen when an excited atom passes through a gas

How does it work?

1) Atom absorbs a certain amount of energy

2) Atom moves to a higher energy level (now called "excited")

3) Moves back down to its normal energy level (Ground State)

    - emits a packet of energy (quanta or photon) as it does this

4) We can see this emission of energy

    - comes out as color!

Photoelectric Effect

- Metals heat up and change color

- Max Planck wanted to explain this change of color

  * determined that energy changes in set units (quanta)

- Planck's Constant

  * Pertains to amount of energy released when an excited electron goes back to its Ground State

  * States: The amount of radiant energy (E) absorbed or emitted is proportional to the frequency of the

     radiation absorbed.

Planck's Constant = 6.6262 x 10 ^-34 Js

Websites:
Click Here for an explanation of quanta, or photon.
Click Here for an explanation of Planck's Constant.
Click Here for the history and explanation of Planck's Constant.