Title: Valence Electrons
Objectives
1. Create a shell model diagram of an atom, placing the correct number of electrons in the correct shells.
2. Explain the difference between a valence electron and a core electron.
3. Describe the patterns in the periodic table associated with electron arrangements, specifically valence
electrons.
Teacher notes and overview of daily lessons
In the shell model, electrons occupy distinct areas around the nucleus of an atom. The electrons in the
outermost electron shell of the atom are called valence electrons. All other electrons are called core electrons.
The periodic table reflects the predictable patterns found in electron arrangements. Among main group
elements, elements in the same group have the same number of valence electrons.
Detailed Daily Plan
Day 1
Warm-up/Entry Task
The atomic number of Carbon is 6. Draw a model of the carbon atom.
How did you decide where to put in the electrons?
Materials (per group of 2 students)
 p. 70 Handout from Living by Chemistry Teaching and Classroom Masters Units 1-3
 1 sheet of paper to “model” electron shells
 Bean Electrons Worksheet
 Beans to represent electrons (30 beans per group)
 Cup for holding electrons
Activity Procedure
Direct Instruction
1. The placement of electrons in atoms is extremely important to understanding how different elements
behave. We’ll be learning about the patterns of how electrons are arranged in atoms.
2. Show visuals of the Shell Model (p. 72), and explain that these are 2-D and 3-D visualizations of where
an electron or group of electrons are most likely to be found.
3. Define electron shells: the levels around the nucleus where electrons can be found.
4. Explain that students will be looking for patterns in the arrangements of electrons and creating shell
models based on these patterns.
5. Model and elicit ideas on how to fill electrons into electron shells using Hydrogen, Helium, Lithium,
and Boron.
Pair Work – Filling in Table of Electron Shells (p. 70 from Living By Chemistry Masters Units 1-3)
1. Examine your periodic table. What patterns do you notice in the number of electrons? What patterns do
you notice in the number of electrons in each shell? Look ACROSS each row and DOWN each column.
2. Using your bean and paper model, demonstrate how the electrons for Beryllium might look. Draw this
into your periodic table.
3. Repeat Step 2 for the remaining blanks.
Based on your handout, what do lithium, sodium and potassium all have in common?
If you know what group an element is in, what can you predict about its electron arrangement?
How can you determine the arrangement of an element’s electrons from its position in the periodic table?
Exit Ticket
What patterns did you notice in the number of electrons and electrons in each shell?
Day 2
Warm-up/Entry Task
Show p. 71 from Living by Chemistry Teaching and Classroom Masters Units 1-3.
 What do you notice about the number of spokes on the circles?
o The number of spokes increases as you go from left to right
o The number of spokes stays the same as you go from top to bottom of a row
 The spokes represent electrons. Do the spokes represent the total number of electrons? Explain your
thinking.
o No – for example, sodium has 11 electrons but only 1 spoke.
Materials (per student)
 Valence Electrons Worksheet (Modified from Life on the Edge Student handout p. 68-69)
 Table of Valence and Core Electrons handout (p. 73)
Activity Procedure
Direct Instruction
1. Define valence electrons, core electrons, and electron shells.
a. Electron shells: levels around the nucleus where electrons can be found. Represented by
spheres or circles.
b. Valence electrons: The electrons located in the outermost electron shell of an atom.
c. Core electrons: all other electrons in an atom besides the valence electrons.
2. Go back to visual of Shell Model and identify valence and core electrons.
Student worksheets
Students fill out Valence and Core Electrons Worksheet.
Exit Ticket
How many valence electrons does rubidium have (Rb)? How do you know?
Bean Electrons
Name _____________________ Per. ______
1. Examine your periodic table. Discuss with your partner: What patterns do you notice in the number of
electrons? What patterns do you notice in the number of electrons in each shell? Look ACROSS each
row and DOWN each column.
2. Using your bean and paper model, demonstrate how the electrons for Beryllium might look. Draw this
into your periodic table.
3. Repeat Step 2 for the remaining blanks.
Based on your periodic table, what do lithium, sodium and potassium all have in common?
___________________________________________________________________
___________________________________________________________________
What does the group number (1A, 2A, 3A, etc.) tell you about the electrons for that group of elements?
___________________________________________________________________
___________________________________________________________________
How can you determine the arrangement of an element’s electrons from its position in the periodic table?
___________________________________________________________________
___________________________________________________________________
Bean Electrons
Name _____________________ Per. ______
1. Examine your periodic table. Discuss with your partner: What patterns do you notice in the number of
electrons? What patterns do you notice in the number of electrons in each shell? Look ACROSS each
row and DOWN each column.
2. Using your bean and paper model, demonstrate how the electrons for Beryllium might look. Draw this
into your periodic table.
3. Repeat Step 2 for the remaining blanks.
Based on your periodic table, what do lithium, sodium and potassium all have in common?
___________________________________________________________________
___________________________________________________________________
What does the group number (1A, 2A, 3A, etc.) tell you about the electrons for that group of elements?
___________________________________________________________________
___________________________________________________________________
How can you determine the arrangement of an element’s electrons from its position in the periodic table?
___________________________________________________________________
___________________________________________________________________
Valence and Core Electrons Worksheet
Name: _________________________________ Per: ___
Fill in the table below.
Element
Total
electrons
Helium
2
Valence
electrons
2
6
Number
of shells
Draw a model
1
2
2
3
Rubidium
1. List three things that all the atoms of the elements in period (row) 3 have in common.
2. Look at your periodic table, and then at yesterday’s handout titled “Table of Electron Shells”. Explain
why the number of electrons in the third shell suddenly changes from 8 to 18 between the element
calcium (Ca) and the element gallium (Ga).
3. If you finish early: Predict the electron arrangement of tin (Sn). Draw a shell model of it and explain
your reasoning.