Name:
Date:
3.4
Topic: Valence Electrons and Lewis Dot Structures
Learning Objectives:
 I CAN determine how many valence electrons an element has from looking at the periodic table
 I CAN draw the Lewis Dot Structure for any element in groups 1-2 and 13-18
Bellringer:
1. Use the periodic table and pattern on the board to draw the Bohr Model and electron configuration
for: MAGNESIUM
Bohr Model:
Electron Configuration: _____________________________
Notes: Lewis Dot Structures
Key Point 1: What is a valence electron?
 Valence electrons are the __________________ electrons (found on the outer energy level)
 The maximum number of valence electrons that an element can have is _____________
o This is because valence electrons only come from the ___ and ___ orbitals (never the d or f)
Key Point 2: What is the trend for valence electrons on the periodic table?
 The periodic table is arranged so that the ______________ determines the number of valence
electrons
o For groups #1-2, the group # = the valence electrons (ex. Ca has 2 valence electrons because
it’s in group 2)
o For groups #13-18, the group # - 10 = the valence electrons (ex. Br has 7 valence electrons
because 17-10=7)
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
The transition metals in groups #2-12 all have ___________ valence electrons
Key Point 3: Why are valence electrons important?
 Valence electrons can be lost or added to an elements outer energy levels
o Elements lose or gain enough electrons to get 8 valence electrons by bonding with other atoms
to either donate, steal, or share valence electrons
 Elements in the same ___________ share similar chemical properties because they have the same #
of valence electrons
Key Point 4: What is a Lewis Dot Structure?
 A Lewis dot structure is a representation of an element’s _____________________ and its
________________ electrons

Directions for drawing a Lewis dot structure:
1. Write down an element’s _______________________
2. Determine how many ____________________ electrons the element has
3. Draw one ____________ for each valence electron around the element symbol starting at the right
4. Keep each dot __________________ until all sides have one dot- then double up
Examples:
Lithium
Nitrogen
Beryllium
Oxygen
Boron
Carbon
Fluorine
Neon
What does a Lewis Dot Structure show you about an atom? Answer in 2 complete sentences:
Why are the valence electrons in an atom important? Answer in 1 complete sentence:
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Independent Practice:
1. Determine the number of valence electrons for the following elements
a. Calcium ___________
b. Selenium ___________
c. Xenon ___________
d. Zinc ___________
e. Rubidium ___________
f. Cobalt ___________
2. For each group of elements circle the two elements that have the same chemical properties
a. carbon, nitrogen, silicon
b. sulfur, bromine, oxygen
c. helium, neon, hydrogen
d. fluorine, chlorine, neon
e. sodium, magnesium, sulfur
3. Draw the Lewis dot structure for Lithium
4. Draw the Lewis dot structure for Magnesium
5.Draw the Lewis dot structure for Chlorine
6.Draw the Lewis dot structure for Xenon
6. Describe 1 trend or pattern on the periodic table used for determining the number of valence electrons
in an element. Use complete sentences.
7.
a.
Write the electron configuration for Beryllium. ______________________________________
b. How many valence electrons does Beryllium contain? _________________________________
c. Write the electron configuration for Calcium: _________________________________________
d. How many valence electrons does Calcium have? ____________________________________
e. How does the number of valence electrons of Beryllium compare to the number of valence
electrons of Calcium?
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