1. Investigation 5: Picturing Molecules
Smells Unit
Investigation 5: Picturing Molecules
Lesson 3: Connect the Dots
Lesson 2: Honk If You Like Molecules
Lesson 4: Eight is Enough
Lesson 5: Dots, Dots, and More Dots

2. Smells Unit – Investigation II
Lesson 3:
Connect the Dots

3. ChemCatalyst
This is a drawing of the structural formula of a methane molecule. The lines represent bonds. Explain what you think a bond is.
Unit 2 • Investigation II

4. The Big Question
How can Lewis dot symbols help us to understand and predict bonding?
Unit 2 • Investigation II

5. You will be able to:
Draw the Lewis dot symbol for an element and predict how many covalent bonds it will make.
Unit 2 • Investigation II

6. Notes
A covalent bond is a connection that forms between two atoms when those atoms are sharing a pair of electrons between them.
(cont.)
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7. Notes (cont.)
When we draw an atom using dots to represent the valence electrons it is called a Lewis dot symbol.
When we draw a molecule using dots to represent the valence electrons it is called a Lewis dot structure.
(cont.)
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8. Notes (cont.)
Nitrogen, with 5 valence electrons, would be drawn as follows:
The Lewis dot symbol of nitrogen has 3 unpaired electrons & 1 electron pair
This means that nitrogen has 3 electrons that can potentially be paired up with electrons from other atoms.
Unit 2 • Investigation II

9. Notes (cont.)
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10. Activity
Purpose: In this lesson you will begin to understand why atoms connect to each other the way they do. You will be introduced to a tool, called Lewis dot symbols, which will assist you in building molecules and predicting how many bonds an element will have.
(cont.)
Unit 2 • Investigation II

11. C N O F Ne
Si P S Cl Ar
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12. (cont.) (cont.) Group number IV V VI VII VIII Number of bonds
First row elements C N O F Ne
Second row elements Si P S Cl Ar
(cont.)
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13. (cont.)
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14. Making Sense
Based on what you’ve learned in this lesson, explain why the HONC 1234 rule works.
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15. Notes
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16. bonded pair of electrons
Notes (cont.)
Bonded pair = a pair of electrons involved in bonding between two different atoms
Lone pair = a pair of electrons not involved in bonding but are paired up within an atom
A single electron is sometimes referred to as an unpaired electron
lone pair of electrons
bonded pair of electrons
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17. Check-In
Draw the Lewis dot symbol for the element I, iodine. Explain how you arrived at your particular drawing.
How many covalent bonds does iodine make?
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18. Wrap-Up
A covalent bond is one in which two atoms share valence electrons.
In a Lewis dot structure, pairs of unbonded electrons are referred to as lone pairs.
HONC 1234 indicates how many unpaired electrons are associated with hydrogen, oxygen, nitrogen and carbon.
Unit 2 • Investigation II

19. Smells Unit – Investigation II
Lesson 2:
HONC If You Like Molecules

20. ChemCatalyst Examine the following molecules.
What patterns do you see in the bonding of hydrogen, oxygen, carbon, & nitrogen?
menthone
diisobutylamine H
Unit 2 • Investigation II

21. The Big Question
How can HONC 1234 help us to draw structural formulas?
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22. You will be able to:
Determine whether the structural formula of a given molecule is possible.
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23. Notes
HONC 1234 is a simple, catchy phrase reminding us about the bonding of hydrogen, oxygen, nitrogen and carbon
It reminds us how many bonds each element usually makes within a molecule
(cont.)
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24. Notes (cont.)
Double bonds and triple bonds still follow the HONC 1234 rule.
Ex.: the double-bonded oxygen in the menthone molecule is bonded twice to carbon and therefore follows the guidelines.
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25. Activity
Purpose: The purpose of this activity is to give you practice in creating structural formulas from molecular formulas and to help you begin to understand why atoms end up in the specific arrangements we find them in.
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26. Molecular formula #1 — C3H8
Molecular formula #2 — C3H8O
Molecular formula #3 — C3H9N
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27. Making Sense
The third molecular formula has at least three possible structures.
Are these all the same molecule? Explain.
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28. Notes
Molecular formula #1 (the same molecule drawn with 2 different orientations)
(cont.)
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29. Notes (cont.)
Molecular formula #2 (4 different drawings are shown – 3 different molecules are represented)
(cont.)
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30. Notes (cont.)
Molecular formula #3 (4 different drawings are shown – but they represent only 3 different structures)
(cont.)
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31. Notes (cont.)
Molecules are isomers of one another if they have the same molecular formula but different structural formulas
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32. Wrap-Up
HONC 1234 tells us how many times hydrogen, oxygen, nitrogen & carbon bond
When a molecule is oriented differently in space it is still the same molecule
A molecular formula can be associated with more than one distinct structural formula (isomers)
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33. Double Check Your Understanding
Go back to Connect the Dots and answer 1. Making Sense 2. Homework Question 2
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34. Check-In Are the following molecules correct according to HONC 1234?
If not, what specifically is wrong with them?
Unit 2 • Investigation II

35. Smells Unit – Investigation II
Lesson 4:
Eight is Enough

36. ChemCatalyst
Draw the Lewis dot structure for the following covalently bonded molecule. Explain how you arrived at your answer.
Cl2
Unit 2 • Investigation II

37. The Big Question
How can we use Lewis dot structures to help draw structural formulas?
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38. You will be able to:
Predict whether a given compound would be stable and likely to be found in nature.
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39. Notes
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40. Activity
Purpose: In this lesson you will use Lewis dot structures to create structural formulas of molecules containing elements in addition to H, O, N, and C. You will look for patterns in the number of electrons surrounding each atom in a Lewis dot structure in order to develop further understanding of bonding.
Unit 2 • Investigation II

41. (cont.)
Br2
H2S
PH3
SiH4
(cont.)
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42. (cont.)
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43. Making Sense
The noble gases do not form bonds with other atoms (except under very extreme conditions).
Explain why you think this might be true (use your Lewis dot structures).
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44. Notes Atoms of most elements are very reactive
They become stable when they combine with other atoms to form compounds.
The more stable a molecule is, the more likely it will exist in nature
Octet rule: atoms tend to form bonds by sharing valence electrons until 8 valence electrons surround each atom
Unit 2 • Investigation II

45. Check-In
Which of the following formulas satisfy the HONC 1234 rule?
Which of the following formulas satisfy the octet rule?
Which of the following formulas represent stable compounds we might find in the world around us?
a) CH3 b) CH4
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46. Wrap-Up
Elements form bonds by sharing electrons until each atom has the same number of valence electrons as the noble gas in the same row of the periodic table — this is called the octet rule.
Unit 2 • Investigation II

47. Smells Unit – Investigation II
Lesson 5:
Dots, Dots, and More Dots

48. ChemCatalyst
Here are the structural formulas for N2 (nitrogen gas), O2 (oxygen gas), and F2 (fluorine gas). Draw the Lewis dot structures for these three molecules.
Unit 2 • Investigation II

49. The Big Question How do we draw a Lewis dot structure for a molecule?
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50. You will be able to:
Use Lewis dot symbols to draw a possible structure for a C2H4O2 molecule.
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51. Notes Draw Lewis dot symbols for C and two O atoms:
Bring atoms together:
Create double bonds:
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52. Activity
Purpose: In this lesson you will work to create structural formulas for various molecules. You will start with the Lewis dot structures of individual atoms. These atoms can then be arranged in more than one way to create molecules. Finally, structural formulas will be translated from the Lewis dot representations.
Unit 2 • Investigation II

53. (cont.) Unit 2 • Investigation II Start with these atoms…
Draw the Lewis structure for the starting atoms
Add hydrogen atoms to satisfy the octet rule
How many
H’s are needed?
Draw the structural formula for the molecule
Write the molecular formula for the molecule
2 carbon atoms bonded together
1 carbon atom and 1 oxygen atom
1 carbon atom and 1 nitrogen atom
1 carbon atom and 2 oxygen atoms
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54. Making Sense
Explain how HONC 1234 assists you in checking out the structural formulas you create.
Unit 2 • Investigation II

55. Check-In
We know two things about a certain molecule. We know that its molecular formula is C2H4O2 and we know that it has one C=O in it. Using Lewis dot symbols and the octet rule to guide you, draw at least one possible structure for this molecule. (There are 3 possibilities)
Unit 2 • Investigation II

56. Wrap-Up
Atoms can form double and triple bonds to satisfy the octet rule
Unit 2 • Investigation II