1. Electron Configuration Notation with Atomic Structure Review
Chemistry I
Mr. Streeter

2. Bohr’s Atom Model
-Confines electrons in shells
-Electrons loses energy due to movement.
-Electrons can be in certain levels depending of the energy they have.
-The region where we can find the electron with high probability is called the orbital.

3. Nature of the electron
-Thompson’s work show that e- behave like particles.
-In 1924, Louis de Broglie states that e- behave like waves based on Bohr’s model.
-This was explained in the electromagnetic spectrum.

4. Electromagnetic Spectrum
The frequency is mathematically related to the wavelength:
c=λv
Where c=speed of light (3.0 x 108 m/s)
λ= wavelength
v= frequency

5. Electromagnetic Spectrum
All the frequencies or wavelenghts of electric radiation.

6. Electromagnetic Spectrum
-The movement of electrons produced light when received and release energy.
-In 1905, Albert Einstein proposed that light have properties of light and waves.

7. Light Emission

8. Light Emission
Electron in lowest possible energy is in ground state.
Electron that gains energy move to excited state.
Electron release energy as go back to ground state.

9. Light Emission E1=Energy in ground state E2=Energy in excited stated.
Overall energy= E1-E2

10. Quantum Numbers
-Number that specifies the properties of the electrons.
-There are 4 quantum numbers: n, , m and ms

11. Quantum Numbers
n= level number (n=1 thru 7).
 (n-1)= Shape and type of orbital
s=0
p=1
d=2
f= 3
m (from – ,0,+)=Magnetic quantum number
ms= Magnetic spin. Only have two possible numbers (+1/2 and -1/2)

12. Electron configurations
-Arrangements of electrons in an atom.
-Each orbital can have only 2 electrons and with different quantum numbers. This is known as Pauli exclusion principle.

13. Electron configuration
Types and shapes of orbitals

14. Electron configuration
Aufbau principle -Electron fill lowest energy levels first.
Ex s<2s<2p<3s<3p

15. Electron configuration
Notations
There are 3 notations:
1) Long notation or electron configuration
1s22s22p6
2) Orbital Notation

16. Electron configuration
3) Shorthand Notation or Noble Gas configuration.
[Ne]3s23p4

17. Electron configuration
Hund’s Rule -For atoms in ground state, the number of unpaired electrons is the maximum possible and have the same spin.

18. Order in which subshells are filled with electrons2p 3p 4p 5p 6p 3d 4d 5d 6d 4f 5f

19. Electron configuration
Example
What is the electron configuration of an element with atomic number of 9 (Z=9)
An element with z=9 is Fluorine.
We start with the less energy level and orbital, so then is 1s22s22p5. The orbital notation will be then

20. Filling Rules for Electron Orbitals
Aufbau Principle: Electrons are added one at a time to the lowest energy orbitals available until all the electrons of the atom have been accounted for.
Pauli Exclusion Principle: An orbital can hold a maximum of two electrons. To occupy the same orbital, two electrons must spin in opposite
directions.
Hund’s Rule: Electrons occupy equal-energy orbitals so that a maximum number of unpaired electrons results.
*Aufbau is German for “building up”

21. General Rules Pauli Exclusion Principle
Each orbital can hold TWO electrons with opposite spins.
Courtesy Christy Johannesson

22. General Rules Aufbau Principle6d 5f 7s 6d 5f
Aufbau Principle
Electrons fill the lowest energy orbitals first.
“Lazy Tenant Rule” 6p 7s 5d 4f 6p 6s 5d 5p 4f 6s 4d 5s 5p 4d 4p 5s 3d 4s 4p 3d 3p 4s
Energy 3p 3s 3s 2p 2s 2p 2s 1s 1s
Courtesy Christy Johannesson

23. General Rules WRONG RIGHT Hund’s Rule
Within a sublevel, place one electron per orbital before pairing them.
“Empty Bus Seat Rule”
WRONG
RIGHT
Courtesy Christy Johannesson

24. 1s2 2s2 2p4 O Notation 1s 2s 2p 8e- O Orbital Diagram 8
Notation
Orbital Diagram 1s 2s 2p O
8e-
Electron Configuration
1s2 2s2 2p4
Courtesy Christy Johannesson

25. S 16e- 1s2 2s2 2p6 3s2 3p4 S 16e- [Ne] 3s2 3p4 Notation Core Electrons
32.066 16
Notation
Longhand Configuration
S 16e-
1s2
2s2
2p6
3s2
3p4
Core Electrons
Valence Electrons
Shorthand Configuration
S 16e- [Ne] 3s2 3p4
Courtesy Christy Johannesson