1. Notes #3: History of the Atom (Part 3)
WCHS Chemistry

2. RUTHERFORD

3. WRONG! Correct :) NEILS BOHR (1919) Bohr Model of the Atom
Electrons orbit around the nucleus like planets around the sun
Each orbit is a different energy level:
Farther from nucleus → greater energy
Highest Energy
WRONG! 4 3 2 1
Nucleus
Correct :)

4. PROBLEMS!!! NEILS BOHR (1919) Bohr Model of the Atom
Bohr’s model incorrectly said:
E- are in specific places
We can predict where orbits are

5. Discovered the neutron Must have a neutral “buffer”
JAMES CHADWICK (1932)
Discovered the neutron
Must have a neutral “buffer”

6. BOHR’S MODEL VS. FLAME TESTS
There are 2 states for an electron to be in:
Ground State vs. Excited State
Low energy e- picture
ADD ENERGY
e- gain energy to jump up to higher energy levels
e- as close to nucleus as possible e- e- e- e- e- e- e- e-

7. BOHR’S MODEL VS. FLAME TESTS
Then, they fall back down to their original orbit, releasing that energy as a photon of light.
See light!!
Photon
We see photons of light Different amounts of energy are different colors!
Bohr’s model could predict these colors, but it only worked well for hydrogen -- why?
B/c Hydrogen is so simple! → only 1 electron!

8. WHITE LIGHT Lowest Energy Highest Energy
We see different colors of light due to different amounts of energy!

9. HYDROGEN EMISSION SPECTRUM
You will see a “bar code”
Every “bar” on the code is an electron releasing a photon when it falls back down from an excited state to ground state.

10. HELIUM EMISSION SPECTRUM

11. NITROGEN EMISSION SPECTRUM

12. NEON EMISSION SPECRUM