1. The Bohr Model

2. Niels Bohr created 1st model of the atom
Want to explain excited atoms & and the line-emission spectrum
But TOO simple
Still useful however!
Helped us to develop the current model of electron activity – the “quantum model”

3. The Bohr Model Thought electrons orbited like planets
Thought that when an atom is “excited”, they jump up into higher orbits
“what goes up, must come down”
Come down– they lose energy and ???
Excited electron absorbs heat (gains energy)and jumps up to a higher-level orbital
Then the electron falls back to a lower level orbital . Since energy can’t disappear, the energy lost by the electron as it falls down is released as light.
Photon of light is emitted – this is what we see as the color of the burning element !

4. The Bohr Model More orbitals = more energy states!
Big jumps = Bigger Energy!
Small jumps = smaller energy (lower freq)
Remember E=hν
Can determine the relative energy levels of the orbitals by looking at the energies of the photons emitted

5. Good & Bad about the Bohr Model
Great for explaining the line-emission spectrum of hydrogen
Not great for everything! More complex atoms don’t work! New model needed!
Was right about the line-emission spectra & using it to see electron configurations
BIG PROBLEM! Electrons don’t orbit like planets
Modern model developed, called the “quantum model of the atom”

6. Students Being the "Bohr"
The Atom Song

7. The Quantum Model of the Atom
Electrons don’t go around like planets -- found in clouds
Clouds are called “orbitals”
Electron movement is random but it has to stay in its own orbital
Excited electrons jumping between orbitals = light emitted
Orbitals are described by their shape, the energy level they are on, and their orientation.

8. Orbital Shapes Four types of orbitals Shapes:
Called the “s”, “p”, “d” and “f”.
Nucleus is at the center of each orbital
Each orbital can hold a maximum of two electrons
Shapes:
s orbitals = spherical clouds
p orbitals = figure eight clouds
Most d orbitals = cloverleaf clouds
F orbitals are very complicated and we won’t be drawing them
= electron
Video of Orbitals

9. Orbital Energy Levels Orbitals exist on different energy levels
7 possible energy levels: 1,2,3,4,5,6, and 7.
Higher energy levels = farther from the nucleus
1s orbital is a spherical cloud close to the nucleus
7s orbital is a spherical cloud far from the nucleus.
Not all types of orbitals exist at each energy level
Nucleus
1s cloud
7s cloud
“1s” electrons
“7s” electrons

10. Orbital Orientations S orbitals - one orientation
At each energy level only 1 s orbital
P-orbitals -3 orientations
P orbitals =figure eights
Can fit 3 around the nucleus
1 horizontally (the “x orientation”)
1 vertically (the “y orientation”)
1 that goes in & out (the “z orientation”)
D- orbitals- 5 orientations
F orbitals- 7 orientations

11. Electron “Spin” 2 electrons can be in each orbital
i.e. the 3s orbital holds two electrons, the 4Px orbital holds two, the 4Py orbital holds two, etc.
In the same orbital – Electrons have opposite magnetic “spins”
one spins “up” and the other spins “down”.

12. Putting it all together
How does an electron “live”
Can talk about:
Energy Level
Shape
Orientation
Spin
For example
lives in the “3Py” orbital and spins up
lives in the “3Px” orbital and spins down
nucleus

13. The Final Information:
So how many electrons does a particular atom have, and which orbitals are they found in?
# of electrons in an uncharged atom = # of protons (remember?)
which orbitals the electrons are found in - will take a bit longer to answer.
Time to learn about the “Atom’s Family!”
So how many electrons does a hydrogen atom have? 1
Oxygen? 8
Carbon? 6
Sodium? 11