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Lesson Plan Chemistry
Katie Pozivilko
Cornerstone University
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Lesson Plan Chemistry
Purpose:
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For students to understand how to correctly draw a Lewis structure for any
compound.
For students to learn how to correctly draw Lewis structures of compounds with
resonance structures.
Objectives:
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Given a periodic table and prior knowledge of calculating valance electrons
students will be able to correctly draw a Lewis structure for any compound.
Given a periodic table students will be able to correctly draw Lewis structures of
compounds with resonance structures.
Review:
The following items were taught in previous lessons:
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Terms: Valance electron, Element, Compound, Electron, Proton, Atom,
Negative/Positive charge, and Central atom.
How to calculate the correct amount of valance electrons around a compound.
How to calculate the correct amount of valance electrons around a negatively or
positively charged compound.
How to correctly draw the Lewis structure for a single atom.
Anticipatory Set:
For the anticipatory set, show the students the YouTube video, “Drawing Lewis Dot
Diagrams” by bozemanbiology. Before the movie, explain to the students that the video shows
how to draw Lewis Structures and that the first part will be a review and that they will watch
the second part in a few minutes after they have learned how to draw the compound structure.
Start the video at 2 minutes 40 seconds and watch till they get to the part about the
compounds. After the video review the four quadrant idea again.
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Input:
New terms:
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Resonance structures- a way of describing delocalized elections within
certain compounds that can be drawn in multiple ways (Resonance).
Delocalized electrons- are electrons in compounds, ions, and metals that
are not associated with a single atom or bond (Delocalized).
The students do not know how to draw the Lewis structures for compounds yet. So, first
review how to find the number of valance electrons in a compound and how to draw the dot
diagram for the individual atoms in the compound by doing one or two examples on the board
(examples below). Then, explain to students how to draw a Lewis structure for the compounds.
Tell them to draw the individual dot diagrams for the atoms placing the atoms around the
central atom. Tell the students that instead of using dots for the central atom use X’s. Next,
have the student’s pair one of the unpaired electrons on the outer atoms with one of the X’s of
the central atom. Have the students erase the dot and X and have them draw a line instead.
Explain how that the line represents a bond formed between the atoms (steps shown in video).
Show them the completed drawing of the compound and then have them try the next
compound on their own before showing the correct drawing.
Define a resonance structure (a resonance structure is a way of describing delocalized
elections within certain compounds that can be drawn in multiple ways (Resonance)), then
show them how to draw resonance structures (examples below). Explain to the student that a
compound that would have resonance structures have delocalized electron. Delocalized
electrons are electrons in compounds, ions, and metals that are not associated with a single
atom or bond (Delocalized). The different ways to draw that compound is called drawing its’
resonance structures. Help the students through an example up on the board. Explain to the
students that the atoms can be double bonded to each other. Teach the students that most
resonance drawings only differ in that the double bond in the compound can be shown being
formed between multiple atoms. After showing them an example, have them try one on their
own. After they have all tried to draw the compound resonance structure show them the rest
of the video from earlier in the anticipatory set.
Review examples of how to find the number of valance electrons in a compound and dot
diagram:
CCl4
C=4, Cl=7
4+7(4)= 32
NH3
N=3, H=1
3+1(3)=
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Example of how to draw Lewis structures:
Show steps on board:
Independent:
BF3
H2O
Examples of resonance structures:
Show steps on board
NO3-
Independent:
CO3^2-
Modeling:
For better understanding of what the compound will look like in 3D, grab a molecular
model kit (I keep them in the back cupboard in the drawer labeled “molecular model kits”).
Show the students what a few of the examples from the list above by recreating them with the
kit and showing them what the compound looks like and explain a bit about the shape. The
angles of the central atom will depend on the number of valence electrons it has. We will be
going into shapes next week. Below is a picture of what the molecular model kits look like:
(Advanced Molecular Model Kit)
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Checking for Understanding:
To check for understanding, ask the students questions as you put together one of the
3D example compounds. How many valance electrons does the central atom have (answer
indicated in example drawing)? What molecular model piece do I need to represent the central
atom (answer will depend on number of valance electrons which should be indicated next to
example drawing)? How many valance electrons does the bonding atom have (answer indicated
in example drawing)? Does this compound have any double bonds? And ask any other
questions that come to mind. Have students raise their hands and answer the questions orally.
Guided Practice:
Have the students get into groups of about three people and have one of the students
go and get a molecular model kit for the group. Walk them though the steps of making one
example compound then give them another compound from the examples and give them a
moment to try it themselves before showing them how to make the compound. Tell the
students that through the activity they are learning the first objective on how to create a Lewis
structure and that it will help them because they will be able to see the structure in 3-D. It will
help the student to play with the molecule structures and attempt to arrange them in correct
ways. Making the 3-D model will help them to see the compound better and be able to draw
understand the structure of the compound and why it is formed the way it is.
Independent Practice:
After they have the hang of making the 3D structures, hand out a sheet labeled
“Molecular Model Compound Sheet.” Have the students create, draw and calculate valence
electrons for each of the compounds indicated on the sheet. Have them complete one model at
a time and have them raise their hand and show that they have created, drawn, and calculated
the number valence electrons correctly before they can move on to the next. There will be a
blank on the sheet next to the compound that the teacher must check off before they can
continue on to the next compound. Before putting the check on the sheet, ask the students
what their central atom is and how many valance electrons the compound has (answers to
questions will be on answer sheet).The students should reply orally. Have them complete the
sheet and turn it in before the end of class.
Closure:
Do a quick review asking the students what a resonance structure is (a resonance
structure is a way of describing delocalized elections within certain compounds that can be
drawn in multiple ways (Resonance)), if they now know how to draw a compound Lewis
structure, and if they have any final questions. The students should reply orally. If they want an
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extra example of drawing either a compound or resonance structure, use one or both of the
following:
Compound
Resonance structure
CH4
O3
Assessment:
The assessment will be the worksheet done in class. If they got all the compounds
checked off they get full points for the day’s lesson.
Homework:
There will be a packet to hand out, but tell the students that they are not due till Friday.
The packet is labeled, “Lewis Structures,” and should be on my desk. The answer sheet will also
be on my desk for if the students have questions.
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References
Advanced Molecular Model Kit (n.d.). In Nasco Dedicated to Delivery. Retrieved April 3, 2013,
from
http://www.enasco.com/product/SB33502M
Andersen, . (2010, October 17). Drawing Lewis Dot Diagrams. In YouTube. Retrieved March 31,
2013,
from www.youtube.com
Delocalized electrons (2013, March 30). In Wikipedia. Retrieved February 26, 2013, from
http://en.wikipedia.org/wiki/Delocalized_electron
Neil, J. (2004). Constructing Chemistry Teaching Chemistry by Guided Inquiry (pp. 67-69).
Resonance (chemistry) (2013, March 30). In Wikipedia. Retrieved April 3, 2013, from
http://en.wikipedia.org/wiki/Resonance_(chemistry)
Molecular model idea came from my 10th grade Honors Chemistry class