1. Electron Configuration
12/14/09
Cornell Notes
Stations Practice

2. What we have learned so far…
How to write electron configurations
How to find the number of valence electrons in an element

3. What we are learning today…
What info we can get from valence electrons?
What’s an easier way to write the electron configuration?
Why?
Electron configurations help us predict how elements behave!

4. Valence Electrons O8 1s2 2s2 2p4
Valence electrons are electrons in the HIGHEST ENERGY LEVEL
How many valence electrons are in oxygen? O8
1s2
2s2
2p4
8 valence electrons!

5. Valence Electrons Why are they important? They tell us:
the chemical properties of an element
The group an element is in
Elements in same group
 same number of valence electrons  similar chemical properties

6. Example:
How many valence electrons do oxygen (O), sulfur (S) and selenium (Se) have?
6 valence electrons! 1 8 2 3 4 5 6 7

7. Example Using the table below, what are the identity of the element?
Number of electrons
Energy Level 1 2
Energy Level 2 8
Energy Level 3 3

8. Noble Gas Configuration
A shorter way to write electron configurations! Electron configuration of Bromine (Br) Br
1s2 2s2 2p6 3s2 3p6
4s2 3d10 4p5
1s2 2s2 2p6 3s2 3p6
[Ar]

9. Noble Gas Configuration
Steps:
Find the element on the periodic table
Identify the noble gas that came before it
Write the noble gas symbol in brackets
Write the rest of the electron configuration

10. Example
Using noble gas notation, write the electron configuration of Sulfur (S)
[Ne]
3s2
3p4 1 2 1 2 3 4 3

11. Practice Worksheet Task: Complete the problems on the worksheet
You may work in groups
If you do not finish in class, finish it as homework TONIGHT
We will check the answers tomorrow.