12/14/09
1. Cornell Notes
2. Stations Practice
What we have learned so far…

How to write electron configurations
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How to find the number of valence
electrons in an element
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!
Valence Electrons
Valence electrons are electrons in the
HIGHEST ENERGY LEVEL
How many valence electrons are in oxygen?
O8
1s2 2s2 2p4
8 valence
electrons!
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
Example:
How many valence electrons do oxygen
(O), sulfur (S) and selenium (Se) have?
1
2
6 valence
electrons!
8
3 4 56 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
Noble Gas Configuration
A shorter way to write electron
configurations!
Electron configuration of Bromine (Br)
Br
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
[Ar] 1s2 2s2 2p6 3s2 3p6
Noble Gas Configuration
Steps:
1. Find the element on the periodic table
2. Identify the noble gas that came before
it
3. Write the noble gas symbol in brackets
4. Write the rest of the electron
configuration
Example
Using noble gas notation, write the electron
configuration of Sulfur (S)
1
3
2
[Ne] 3s2 3p4
1234
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.
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