Catalyst: 10.27.2008
Find the atomic #, mass #, # protons, # electrons, and #
neutrons for the following elements:
Beryllium & Lithium
Objective
 Explain how electrons are placed in the electron cloud.
 Identify valence electrons
 Make atomic diagrams with proper electrons
 Construct Lewis Dot Diagrams to show valence
electrons
Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008
Electron Location
 Where are electrons located in an atom?
 Outer electron cloud
 What do they do there?
 Constantly moving
 How are they arranged in the electron cloud?
 In a specific pattern called energy shells (or levels)
Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008
Electron
Location
-e- constantly moving & found in electron
cloud
- arranged in energy shells/levels
Energy Shells
 Each shell or level has a specific amount of energy (E)
 Each shell can only hold a certain amount of electrons.
Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008
Electron
Location
-e- constantly moving & found in electron
cloud
- arranged in energy shells/levels
- each level has specific amt. of energy
Energy
Shells/Lev
els
Energy Shells
 Each energy shell/level is represented by a circle around
the nucleus of the atom.
 The first (lowest) energy level holds only 2 electrons
 After this level is filled up,
electrons go to a higher (outer)
E level.
 Electrons fill the lower levels and
then move to higher (outer) levels.
Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008
Electron
Location
-e- constantly moving & found in electron
cloud
- arranged in energy shells/levels
- each level has specific amt. of energy
Energy
Shells/Lev - 1st energy level: 2 e- maximum
- after a level is filled up, e- go to higher
els
(outer) energy levels
Energy Shells
 No matter how many energy levels there are, the
outermost energy level can only hold at most 8 electrons
 The outermost energy level is called the valence shell.
Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008
Electron
Location
-e- constantly moving & found in electron
cloud
- arranged in energy shells/levels
- each level has specific amt. of energy
Energy
Shells/Lev - 1st energy level: 2 e- maximum
- after a level is filled up, e- go to higher
els
(outer) energy levels
- valence shell – outermost energy level /
can hold @ most 8 e-
Energy Shell Example
(Left page)
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Carbon:
What is its symbol?
What is the atomic number?
What is the atomic mass?
How many protons does it have?
How many electrons does it have?
How many neutrons does it have?
How many electrons go in the first shell?
How many electrons go in the next shell?
How many valence electrons are there?
Energy Shell Example
(Left page)
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Carbon:
What is its symbol? C
What is the atomic number? 6
What is the atomic mass? 12
How many protons does it have?
How many electrons does it have?
How many neutrons does it have?
How many electrons go in the first shell?
How many electrons go in the next shell?
How many valence electrons are there?
Energy Shell Example
(Left page)
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Carbon:
What is its symbol? C
What is the atomic number? 6
What is the atomic mass? 12
How many protons does it have? 6
How many electrons does it have? 6
How many neutrons does it have?
How many electrons go in the first shell?
How many electrons go in the next shell?
How many valence electrons are there?
Energy Shell Example
(Left page)
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Carbon:
What is its symbol? C
What is the atomic number? 6
What is the atomic mass? 12
How many protons does it have? 6
How many electrons does it have? 6
How many neutrons does it have? 6
How many electrons go in the first shell? 2
How many electrons go in the next shell? 4
How many valence electrons are there? 4
Energy Shell Example
(Left page)
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Carbon:
What is its symbol? C
What is the atomic number? 6
What is the atomic mass? 12
How many protons does it have? 6
How many electrons does it have? 6
How many neutrons does it have? 6
How many electrons go in the first shell? 2
How many electrons go in the next shell? 4
How many valence electrons are there? 4
Energy Shell Example #2
(Left page)
 Draw an atomic diagram for Helium.
 How many valence electrons are there in Helium?
Energy Shell Example #2
(Left page)
 Draw an atomic diagram for Helium.
e2 p+
2 n0
e-
 How many valence electrons are there in Helium?
2e-
Lewis Dot Diagrams
 Lewis Dot Diagrams are a way to show you how many
valence electrons are in an atom.
 How many valence electrons were in Carbon?
 4 valence e Lewis Dot Diagram of Carbon:
Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008
Lewis Dot
Diagram
-Show how many valence electrons in an
atom.
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Lewis Dot Diagram
Practice (Left Side)
 Draw the Lewis Dot Diagram for each of the following:
1. Element X has 2 valence electrons.
2. Element Y has 5 valence electrons.
3. Element Z has 7 valence electrons.
Practice Problems
 You will create an atomic diagram with correct number
of energy levels AND a Lewis Dot diagram for each of
the of following elements:
Boron, Nitrogen, Phosphorous, Chlorine, and Fluorine.
e2 p+
2 n0
e-