1. Electron Configurations
Chapter 4

2. Aufbau Principle
Electrons occupy the lowest energy level orbital that can receive them

3. Electron Configuration
The order and arrangement of electrons in an atom

4. 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p 8s
This is the order used to place electrons- follow the arrows to their “end”, then move to the next arrow

5. Hund’s Rule
Orbitals of equal energy are each occupied by one electron before being occupied by a second electron
All electrons in “single orbitals” must have the same spin state

6. Orbital Notation
Use groups of boxes or lines to designate the sub-orbitals within 1 orbital
Arrows are used to represent electrons occupying these boxes AND their spin state

7. Electron Arrangement Aluminum (13) Scandium (21) Potassium (19)
1s2 2s2 2p6 3s2 3p1
Scandium (21)
1s2 2s2 2p6 3s2 3p6 4s2 3d1
Potassium (19)
1s2 2s2 2p6 3s2 3p6 4s1

8. Noble Gas Arrangements
Aluminum (13)
[Ne] 3s2 3p1
Scandium (21)
[Ar] 4s2 3d1
Potassium (19)
[Ar] 4s1