ChemistryValence Electrons

Mrs. McLeod

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

Quick Way for Valence E-

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

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

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

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

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

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

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

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

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!**

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-

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

Nitrogen - Answer

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

Al - Answer

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

F - Answer

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

Ne - Answer

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

Si - Answer

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

Click here once you have done all practice problems

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)

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

Example – Dot Structure for O

• Step 1: O has 6 valence electrons

OStep 2: Write chemical Symbol

Example – Dot Structure for O

O

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

= e-Place one in each direction first

Double up electrons now This is the correct answer!!!

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

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Hydrogen Answer

HNote: You can place the electron in any direction you like when you have less than 4 electrons

Ne Answer

Ne

P Answer

P

Ca Answer

Ca

Al Answer

Al

• Practice worksheet!!! Valence Electrons and Dot structures

• Interactive Periodic table Smart Board

• Periodic Table Basics

• Review Game