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Lesson 2-6 Trends: Valence Electrons and Attractive Force
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Debra Knickerbocker 8 months, 4 weeks ago
Chemistry | Atomic Model |
Lesson 2-6 Trends: Valence Electrons and Attractive Force
Time
Developing the Ideas--Lesson
Engaging the
Student (Entry
Task)
2 class DAY 1: Warmperiods up Questions
1. What two
subatomic
particles
have
charges?
List the
particle
name
and its
charge.
2. What
does the
term
“neutral”
mean?
3. Describe
which
particles
and how
many of
each you
need to
make a
neutral
beryllium
atom.
4. The
atomic
number
of
Carbon
is 6.
Draw a
model of
the
carbon
atom.
(4 minutes)
How did you
decide where
Student
Handout
Teacher/Lesson Notes
Day 1
Student
Handout
Learning Targets:
DAY 1:
Students will continue to gain an understanding of the
interplay between the attractive/repulsive forces of an
Day 1
atom.
Homework (half
Students will be able to describe the patterns in the
sheet)
periodic table associated with electron arrangements.
Students will develop a Bohr model of atoms.
Day 2
DAY 2:
Student
Students will understand the difference between
Handout
valence and core electrons.
Students will understand how ions form.
DAY 1--TEACHER INSTRUCTIONS:
1. Have students answer the warm up questions. They will
refer back to their answers at the end of the period.
2. Introduction “Yesterday you were introduced to the idea of
the energy levels (electron shells). Today we will be using
that knowledge to look at the electrons of each element, and
how they are arranged around the nucleus. The placement of
electrons in atoms is extremely important to understand how
different elements behave.”
3. Remind students about the electron shells, or the levels
around the nucleus where the electrons can be found.
Remind student that they learned that the energy shells have
a certain number of electrons that can fit around the nucleus
in that shell. Based on experiments, we know that electrons
are not ‘falling inward’ towards the nucleus. Remind students
that the proton number determines what the element is.
4. Discuss the Shell Model (the top part of the student
handout), showing that each atom has electrons around the
nucleus in three dimensions. This is a representation of the
Bohr model and there is a convention that allows scientists to
draw the electrons of atoms. Model and elicit ideas on how to
fill electrons into the electron shell drawings for Hydrogen,
Helium, Lithium and Boron.
5. Have students work in pairs to complete the periodic table
on the student handout. The students will look at the
representations of elements present and determine the
trends to fill in the missing elements first using beans to put
the electrons into the correct shells (Use the class handout
Materials
Checking for
Understanding
(exit ticket)
30 beans for
each
partnership.
DAY 1:
Half-sheet of
Homework
Handout
One copy of the
Classroom
Handouts for
each
partnership.
Lesson
2-6 Day 1
Student
Handout
Trends
Valence
electrons
and
Attractive
Force
Lesson
2-6 Day 1
Homework
Trends
Valence
electrons
and
Attractive
Force
Lesson
2-6 Day 2
Student
Handout
Trends
Valence
electrons
and
Attractive
Force
DAY 2: Exit
Ticket
Questions
1. What is the
difference
between
valence and
core model
electrons?
2. What is an
ion? Why do
atoms form
ions?
3. In the past
few lessons,
what trends
have you
noticed in how
the elements
are arranged in
the periodic
table (name
three)?
4. Look back at
the poster from
when you saw
Sodium
“explode”.
What is one
thing that you
can add or
modify for your
explanation?
to put in the
electrons?
DAY 2: Go over
the homework
from day one.
that is the full page orbital shells).
6. Once students are finished with the bean/drawing activity,
go over the correct answers for the elements that had been
missing.
7. Then, pass out the periodic table that features the spokes
on the wheel. (The page is titled Chem Catalyst and is a Class
Handout) Have students compare this periodic table to the
one that they had just worked on.
8. Ask the students:
A. What do you notice about the number of spokes on the
circles?
(Answer – They are equal to the number of electrons in the
outer shell)
B. The spokes represent electrons. Do the spokes represent
the total number of electrons?
(Answer – No, only the electrons from the outer shell)
C. In the past few days, you have learned about the attractive
forces of the protons on the electrons. What would be
‘special’ about these electrons?
(Answer – They have the least amount of attractive forces
acting on them because they are in the shell furthest from
the nucleus.)
9. Define the following terms for your students and have then
write the definitions on the bottom of the handout:
Electron Shells: Levels around the nucleus where electrons
can be found. Represented by spheres or circles.
Valence electrons: The electrons located in the outermost
electron shell of an atom.
Core electrons: All other electrons in an atom beside the
valence electrons.
10. Explain that valence electrons are very important to
describe the chemical properties of the different elements.
They help to determine the type of bonds that each element
will form (to be discussed in the next Big Idea).
11. Show students the homework, which asks students to
draw the electron representations of potassium and calcium
and to identify the valence electrons for the elements on their
handout.
DAY 2--TEACHER INSTRUCTIONS:
1. Continuing from yesterday. Have students bring out their
homework and go over it. Check that students highlighted
the valence electrons for all of the elements on the worksheet
from yesterday. Have students discuss in groups the
questions that were on the homework. Students hopefully
noticed the trends that each column has the same number of
valence electrons and that it goes up by one across the rows.
2. Tell students: “Valence electrons are very important when
looking at elements. These are the elements that are furthest
away from the nucleus, and yesterday, we determined that
these elements have the least amount of attractive force
acting on them by the protons. These electrons are very
important when atoms bond to form compounds or salts"
Let's at the second row of the periodic table. "What do you
notice about valence electrons as you go from left to right?"
(Answer: The number increases by one until the noble gases
which have eight).
The most stable elements, the noble gases, have a full outer
shell. All of the elements either loose or gain electrons to
become more stable. Metals, on the left side of the periodic
table, tend to lose electrons, while non-metals, on the right
side of the periodic table, tend to gain electrons. This is
because of the interplay of the attractive forces of the
protons and the distance of the electrons from the nucleus.
When an atom gains or loses electrons it is called an ion. The
resulting ion is “charged” because the protons and electrons
are no longer balanced. If the ion has more protons than
electrons, it is a positive ion and is called a cation. If an ion
has more electrons than protons, it is a negatively charged
ion and is called an anion.
Today, we will be working with the beans again to help us
understand ions.”
2. Have students work in partners. Students will use the same
Class handout from yesterday – a large version of the
electron shell.
3. Work through one of the elements with students. Use the
idea that the most stable form is that of the nearest noble
gas. Help students to understand that if the elements lose an
electron the resulting ion is positive because it now has more
positively charged particles than negative.
4. Have students fill out the rest of the chart.
5. The final row of the chart asks for students to write the
Element Symbol of the Ion. There is an example given in the
chart but you should bring their attention to it.
6. Bring the students back together at the end of the activity.
Have the chart created from the original lesson. It had
students’ ideas about why the elements reacted differently.
7. Have student’s complete the exit ticket questions.
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