1. Electron configuration
Electrons in Atoms
Electron configuration

3. Electrons
The arrangement of electrons in an atom will determine the chemical and physical properties of that atom (or ion).
Because of this it is important to know where those electrons are (or are most likely to be found)

4. Where do we find electrons?
Electrons in atoms are arranged as
LEVELS (n)
SUBLEVELS (l)
ORBITALS (ml)
Think of these as the electrons address.

5. Energy Level (n)
This tells you how far the electron is from the nucleus, the higher the energy level the further from the nucleus
Currently n can be 1 thru 7, because there are 7 periods on the periodic table

6. Energy Levels
n = 1
n = 2
n = 3
n = 4

7. Sublevels
attempt to describe where the electrons are likely to be found
s, p, d, f
ORBITALS
Found within the sublevels
Each orbital can hold a maximum of 2 electrons

8. Types of Orbitals
The most probable area to find these electrons takes on a shape
So far, we have 4 shapes. They are named s, p, d, and f.
Each orbital has different “flavors”
s= 1 flavor
p = 3 flavors
d = 5 flavors
f = 7 flavors
Each “flavor” can hold a maximum of 2 electrons

11. How many electrons can be in a sublevel?
Remember: A maximum of two electrons can be placed in an orbital.
s orbitals
p orbitals
d orbitals
f orbitals
Number of
orbitals
Number of electrons

12. Electron possible per energy level
2n2 = the number of electrons possible in an energy level
Ex: 3rd energy level, n=3
2(3)2 = 18

13. 2p4 Electron Configurations
Number of electrons in the sublevel
Energy Level
Sublevel
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14… etc.

14. Pauli Exclusion Principle
General Rules
Pauli Exclusion Principle
Each orbital can hold TWO electrons with opposite spins.

15. General Rules Aufbau Principle
Electrons fill the lowest energy orbitals first.
“Lazy Tenant Rule”

16. Diagonal Rule 1 2 3 4 5 6 7 s s 2p s 3p 3d s 4p 4d 4f s 5p 5d 5f 5g?
Steps:
Write the energy levels top to bottom.
Write the orbitals in s, p, d, f order. Write the same number of orbitals as the energy level.
Draw diagonal lines from the top right to the bottom left.
To get the correct order, follow the arrows! 1 2 3 4 5 6 7 s
s 2p
s 3p 3d
s 4p 4d 4f
By this point, we are past the current periodic table so we can stop.
s 5p 5d 5f 5g?
s 6p 6d 6f 6g? 6h?
s 7p 7d 7f 7g? 7h? 7i?

17. General Rules Hund’s Rule WRONG RIGHT
Within a sublevel, place one e- per orbital before pairing them.
“Empty Bus Seat Rule”
WRONG
RIGHT

18. 1s2 2s2 2p4 O Notation 1s 2s 2p 8e- Orbital Diagram
Electron Configuration
1s2 2s2 2p4

19. S 16e- 1s2 2s2 2p6 3s2 3p4 Notation Core Electrons Valence Electrons
Longhand Configuration
S 16e-
1s2
2s2
2p6
3s2
3p4
Core Electrons
Valence Electrons

20. S 16e- [Ne] 3s2 3p4 Notation Noble Gas Valence Electrons
Shorthand Configuration
S 16e-
[Ne]
3s2
3p4
Noble Gas
Valence Electrons

21. Lithium
Group 1A
Atomic number = 3
1s22s1 ---> 3 total electrons

22. Carbon Group 4A Atomic number = 6 1s2 2s2 2p2 --->
6 total electrons

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