Why are electrons important?

• Electrons are responsible for HOW ELEMENTS REACT

• That is why we learned how to:–Write electron configurations–Draw electron orbital diagrams

• When we understand electrons–we can predict how elements will behave

(what we can do with them)–Understand the structure of the periodic table

Valence Electrons

• The specific electrons responsible for the chemical properties of an element

• Electrons in an atoms outermost orbitals

• They are in the highest energy levels

Valence Electrons

• Identify number of valence electrons using…–Electron Shell Diagrams–Electron Configurations–Periodic Table

Electron Shell Diagrams

Electron Shell Diagram

Element Symbol F Cl Br I# Protons

# Total Electrons

# Valence Electrons

997

17177

35357

53537

Electron Shell Diagrams• Rules–Draw the nucleus (label

number of protons)–Determine number of

total electrons–The 1st shell can only hold

2 electrons–The 2nd and 3rd shells can

only hold 8 electrons

9

Fluorine9 protons9 electrons

Electron Shell Diagrams

Electron Shell Diagram

Element Symbol B# Protons

# Total Electrons

# Valence Electrons

5

553

Electron Shell Diagrams

Electron Shell Diagram

Element Symbol C# Protons

# Total Electrons

# Valence Electrons

6

664

Electron Shell Diagrams

Electron Shell Diagram

Element Symbol N# Protons

# Total Electrons

# Valence Electrons

7

775

Electron Shell Diagrams

Electron Shell Diagram

Element Symbol O# Protons

# Total Electrons

# Valence Electrons

8

886

Electron Configuration

1. Write the electron configurationO 1s2 2s2 2p4

2. Circle the subshells in the highest energy levels

O 1s2 2s2 2p4

3. Count the electrons in those orbitalsO 1s2 2s2 2p4

2 4+ = 6

O

Electron ConfigurationElement Symbol Electron Configuration # Total

Electrons# Valence Electrons

Li 1s2 2s1 3 1Be 1s2 2s2 4 2Si 1s2 2s2 2p6 3s2 3p2 14 4

Na 1s2 2s2 2p6 3s1 11 1

Al 1s2 2s2 2p6 3s2 3p1 13 3

S 1s2 2s2 2p6 3s2 3p4 16 6

Periodic Table

7777

3 4 5 61 2

41 3 6

The number of valence electrons is the same for all

elements in a group (column).

Lewis Dot Structures

1.Determine the _______________

_______________________ for

the element.

2.Write the element’s ___________.

number ofvalence electrons

symbol

Lewis Dot Structures

3. Draw _____________________ around the symbol.a. Add a _______ _ dot to the _______ side

of the symbol.b. Continue adding _________ dots

_____________ around the symbol.c. Pair up dots only when _______________

of the symbol has a single dot.

valence electrons

single right

singleclockwise

all 4 sides

Lewis Dot Structures

1. Determine the number of valence electrons for the element.

2. Write the element’s symbol.

3. Draw valence electrons around the symbol.

Mg

Magnesium2 valence electrons

Lewis Dot Structures

1. Determine the number of valence electrons for the element.

2. Write the element’s symbol.

3. Draw valence electrons around the symbol.

Cl

Chlorine7 valence electrons

Element Lithium

# Valence electrons 1

Lewis dot structure Li

Lewis Dot Structures

Element Magnesium

# Valence electrons 2

Lewis dot structure Mg

Lewis Dot Structures

Element Boron

# Valence electrons 3

Lewis dot structure B

Lewis Dot Structures

Element Silicon

# Valence electrons 4

Lewis dot structure Si

Lewis Dot Structures

Element Nitrogen

# Valence electrons 5

Lewis dot structure N

Lewis Dot Structures

Element Oxygen

# Valence electrons 6

Lewis dot structure O

Lewis Dot Structures

Element Chlorine

# Valence electrons 7

Lewis dot structure Cl

Lewis Dot Structures

Element Neon

# Valence electrons 8

Lewis dot structure Ne

Lewis Dot Structures