Chemistry Valence Electrons

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ChemistryValence Electrons

• Mrs. McLeod

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Valence Electrons

• Valence electrons are the outermost electrons.
• The amount of valence electrons an element has
  determines how reactive the element is.
• In general, elements are most stable when they
  have 8 electrons in the last energy level.
• Smart board example

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Quick Way for Valence E-

• The group number tells you the number of valence
  electrons for groups 1-8 A.

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Quick Way for Valence E-

• Consider Li
• Li is in group 1A
• Take the number of the group it is in and that
  tells the number of valence electrons
• Thus, Li has 1 valence electron

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Quick Way for Valence E-

• Consider Be
• Be is in group 2A
• What group number is the element in?
• 2
• Thus, Be has 2 valence electrons

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Quick Way for Valence E-

• Consider B
• B is in group 3A
• What group number is the element in?
• 3
• Thus, Be has 3 valence electrons

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Quick Way for Valence E-

• Consider C
• C is in group 4A
• What group number is the element in?
• 4
• Thus, C has 4 valence electrons

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Quick Way for Valence E-

• Consider N
• C is in group 5A
• What group number is the element in?
• 5
• Thus, N has 5 valence electrons

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Quick Way for Valence E-

• Consider O
• C is in group 6A
• What group number is the element in?
• 6
• Thus, O has 6 valence electrons

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Quick Way for Valence E-

• Consider Cl
• C is in group 7A
• What group number is the element in?
• 7
• Thus, Cl has 7 valence electrons

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Quick Way for Valence E-

• Consider Rn
• C is in group 8A
• What group number is the element in?
• 8
• Thus, Rn has 8 valence electrons
• Helium is an exception to this rule it only
  has 2 electrons!

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Determine the number of val e-

• 1) Rb
• 2) Ne
• 3) I
• 4) Te
• 5) Al
• 6) P
• Check your answers

• Answers
• 1) 1 val e-
• 2) 8 val e-
• 3) 7 val e-
• 4) 6 val e-
• 5) 3 val e-
• 6) 5 val e-

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Determine the number of valence electrons in the
following

• 1) Sodium
• 2) Nitrogen
• 3) Aluminum
• 4) F
• 5) Ne
• 6) Si

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Na - Answer

• 1) IN GROUP 1
• Thus number of valence electrons 1

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Nitrogen - Answer

• 2) IN GROUP 5
• Thus number of valence electrons 5

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Al - Answer

• 3) IN GROUP 3
• Thus number of valence electrons 3

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F - Answer

• 4) IN GROUP 7
• Thus number of valence electrons 7

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Ne - Answer

• 5) IN GROUP 8
• Thus number of valence electrons 8

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Si - Answer

• 6) IN GROUP 4
• Thus number of valence electrons 4

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Valence Electrons Practice

• Click on the link to visit a Quia Website to test
  your number of valence electrons
• http//www.quia.com/quiz/676540.html
• Do this as a group and do your best
• (After quiz, return here and continue)

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Dot Structures

• Dot Structures show the distribution of valence
  electrons around the nucleus
• Rules
• 1) Determine number of valence electrons
• 2) Write chemical symbol
• 3) Distribute one valence electron at a time
• Do not pair (double up) any electrons until there
  is one electron in each of the four directions
• 4) If there are still more electrons, pair up
  electrons once there is one in each of the four
  directions

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Example Dot Structure for O

• Step 1 O has 6 valence electrons

Step 2 Write chemical Symbol
O
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Example Dot Structure for O

• Step 3 Place valence electrons in each of the
  four directions (north, east, south, west)

O
Double up electrons now
This is the correct answer!!!
Place one in each direction first
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Examples for you

• Write Dot Structures for
• 1) H
• 2) Ne
• 3) P
• 4) Ca
• 5) Al

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Hydrogen Answer
H
Note You can place the electron in any
direction you like when you have less than 4
electrons
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Ne Answer
Ne
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P Answer
P
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Ca Answer
Ca
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Al Answer
Al
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• Practice worksheet!!! Valence Electrons and Dot
  structures
• Interactive Periodic table Smart Board
• Periodic Table Basics
• Review Game