1. Electron Configuration
While the nucleus of an atom can be difficult to change, the electrons are a different story. Electrons can be moved around within an atom or transferred between atoms. When atoms transfer electrons, they become ions, with positive and negative charges, and form ionic compounds. Knowing the arrangement of electrons within an atom can help you to predict which ionic compounds will form.
Knowledge of the electron configuration of different atoms is useful in understanding the structure of the periodic table of elements.
The concept is also useful for describing the chemical bonds that hold atoms together.
In bulk materials this same idea helps explain the peculiar properties of lasers and semiconductors.

2. Parts of electron configuration: Energy Level
The specific amount of energy required for an electron to occupy a certain space around the atom.
Referred to using a quantum number (1, 2, 3, 4…) and written n=1, n=2 etc
Think of these as the levels of a house
The atom would be the house

3. Parts of electron configuration: Sublevel (blocks)
An energy level within the principal energy level
Referred to using letters (s, p, d, f)
Think of these as the rooms within the level of a house.

4. Parts of electron configuration: Orbital
The actual electron cloud
Only a maximum of 2 electrons can occupy an orbital.
Think of these as a two person couch or loveseat within a room on a certain level of a house.

5. Parts of electron configuration: The Electrons
Sublevel Information
Sublevel
Number of Orbitals
Number of electrons s 1 2 p 3 6 d 5 10 f 7 14

6. All Together Energy Level Sublevel # of orbitals
# of electrons on sublevel
Total electrons within energy level 1 s 2 p 3 6 8 d 5 10 18 4 f 7 14 32

7. Pyramid of Power

8. Periodic Table-SUBLEVELS
- Notice the number of electrons that fit in a sublevel relates to the block!
- Follow the arrows until you get to your element
- Notice the d block is one energy level behind
- Notice the f block is 2 energy levels behind

9. How to Write an Electron Configuration
Mg: 1s22s22p63s2
Se: 1s22s22p63s23p64s23d104p4
Cr: 1s22s22p63s23p64s23d4

10. Valence Electrons in an Electron Configuration
The valence electrons are the highest s and p orbitals.
1s22s22p63s23p6

11. Noble Gas Electron Configuration
Shortened version of regular electron configuration
Always use the noble gas in the period ABOVE the element that the configuration is written for
Examples:
Carbon—[He]2s22p2
Sodium—[Ne]3s1

12. Complete in your notes
Write a full electron configuration and Noble Gas configuration for each of the following elements.
Phosphorus
Manganese
Yttrium
Platinum

13. Orbital Configurations
We know that electrons are found within the orbital of a sublevel on an energy level.
However, we do not know how the electrons behave within each unique orbital.
To model this, we will use orbital diagrams and the following rules to predict how the electrons are behaving.

14. Aufbau Principle
Each electron occupies the lowest energy level available.
This is demonstrated with our “follow the yellow brick road” chart.

15. Pauli Exclusion Principle
A maximum of 2 electrons can occupy an orbital. However, the electrons must have opposite spin.
Spin is denoted by arrows pointing up or down.

16. Hund’s Rule
This rule deals with the fact the negatively charged electrons repel each other.
Electrons with the same spin will occupy orbitals of the same sublevel before occupying the same orbital with opposite spin.
Can use analogy of loading a bus after a football game—all the big smelly players will fill each single seat first, and only after they are all full will the players start doubling up in the seats