1. Electron Configuration

2. Why we study electrons
Knowing the position of electrons helps us with many topics:
Why chemical reactions occur
Why some atoms are more stable than others
Why some elements react with only certain atoms
Goal for this topic: We want to know how many electrons an atom has, and where they’re located.

3. The Big (actually small) Picture!
“Electron Cloud”
- Energy Levels ( 1 – 7)
- Sublevels (S,P,D,F – Shapes)
- Orbitals (Specific Orientations– X/Y/Z axis)

4. - S Sublevel – Think Sphere
What the orbitals look like…
- S Sublevel – Think Sphere
- P Sublevel – Figure 8
P Sublevel- X Axis
P Sublevel- Y Axis
Nucleus
P Sublevel- Z Axis
S Sublevel

5. Periodic Patterns s p d (n-1) f (n-2) 1 2 3 4 5 6 7 6 7
© 1998 by Harcourt Brace & Company

6. Orbital Diagrams
Orbital Diagrams are Visual illustrations that show the order that electrons will follow as they fill in the electron cloud.
We start from the bottom and work your way up. That symbolizes starting on the first energy level and work outward.

7. General Rules Aufbau Principle
Electrons must fill the lowest sublevel available. (Letters - S,P,D,F)
You cannot skip any sublevels.
It’s like the Alphabet!

8. General Rules Pauli Exclusion Principle
Each orbital (each box on the diagram) can hold only TWO electrons, and the electrons have opposite spins.

9. General Rules WRONG RIGHT Hund’s Rule
Within a sublevel, place one electron in each orbital with the same spin before pairing them with a second electron. - “Empty Seat Rule”
WRONG
RIGHT

10. A Few things to know…
You are drawing arrows, and they represent electrons. (Neon has 10 electrons so you will need to draw 10 arrows.)
Divided up into different sublevels containing a specific number of orbitals. KNOW THIS INFO!
- The S sublevel has only 1 orbital= total of 2 e-
- The P sublevel has 3 orbitals = total of 6 e-
- The D sublevel has 5 orbitals = total of 10 e-
- The F sublevel has 7 orbitals = total of 14 e-

11. Practice -
Fill in the orbital diagram for Magnesium

12. Electron Configuration
An atom’s electron configuration…
Describes the location of electrons within the atom
Identifies the shape of the electron clouds
- regions where the electrons are held.
Uses numbers and letters to describe electrons’ location and which electron cloud it is part of.

13. 1s2 The Format: The “s” tells you the electron’s cloud shape.
In this case it’s a spherically shaped cloud. It is called the s sublevel. Sublevel = Shape
1s2
The “2” simply tells you how many electrons are in this cloud.
The “1” tells you how far from the nucleus the electrons can go.
In this case 2 electrons are creating the cloud.
In this case, its in the 1st energy level, which is the closest level to the nucleus.
Note: Every orbital can only hold 2 electrons. They must have opposite spins.

14. Connection b/w Orbital Diagram and Electron Configuration1s 2s 2p
Electron Configuration
1s2 2s2 2p4

15. Configuration Practice Problems p 1 2 3 4 5 6 7
d (n-1)
f (n-2) 6 7
Zinc:

16. Noble Gas Configuration Steps:
Shorthand Configuration
This is a shorter way to do e- configurations
Steps…
1) Find the noble gas (group 18) that precedes and comes before the element you are doing.
2) To begin, put the symbol of that noble gas in [brackets]
3) Starting with that noble gas, continue the electron configuration until you get to the element in question.

17. 1s2 2s2 2p3 Nitrogen: [He] 2s2 2p3 B. Notation Nitrogen:
Longhand Configuration
Nitrogen:
1s2
2s2
2p3
Valence Electrons
Core Electrons
Shorthand Configuration
Nitrogen: [He] 2s2 2p3

18. C. Shorthand practice
Example - Sulfur
[Ne]
3s2
3p4

19. C. Shorthand practice
Example - Germanium
[Ar]
4s2
3d10
4p2

20. Practice these in shorthand
Tin (Sn) Uranium (U)