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

Smells Unit – Investigation II Lesson 3: Connect the Dots

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

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

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

Notes A covalent bond is a connection that forms between two atoms when those atoms are sharing a pair of electrons between them. (cont.) Unit 2 • Investigation II

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.) Unit 2 • Investigation II

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

Notes (cont.) Unit 2 • Investigation II

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

C N O F Ne Si P S Cl Ar Unit 2 • Investigation II

(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.) Unit 2 • Investigation II

(cont.) Unit 2 • Investigation II

Making Sense Based on what you’ve learned in this lesson, explain why the HONC 1234 rule works. Unit 2 • Investigation II

Notes Unit 2 • Investigation II

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 Unit 2 • Investigation II

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? Unit 2 • Investigation II

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

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

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

The Big Question How can HONC 1234 help us to draw structural formulas? Unit 2 • Investigation II

You will be able to: Determine whether the structural formula of a given molecule is possible. Unit 2 • Investigation II

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.) Unit 2 • Investigation II

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. Unit 2 • Investigation II

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. Unit 2 • Investigation II

Molecular formula #1 — C3H8 Molecular formula #2 — C3H8O Molecular formula #3 — C3H9N Unit 2 • Investigation II

Making Sense The third molecular formula has at least three possible structures. Are these all the same molecule? Explain. Unit 2 • Investigation II

Notes Molecular formula #1 (the same molecule drawn with 2 different orientations) (cont.) Unit 2 • Investigation II

Notes (cont.) Molecular formula #2 (4 different drawings are shown – 3 different molecules are represented) (cont.) Unit 2 • Investigation II

Notes (cont.) Molecular formula #3 (4 different drawings are shown – but they represent only 3 different structures) (cont.) Unit 2 • Investigation II

Notes (cont.) Molecules are isomers of one another if they have the same molecular formula but different structural formulas Unit 2 • Investigation II

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) Unit 2 • Investigation II

Double Check Your Understanding Go back to Connect the Dots and answer 1. Making Sense 2. Homework Question 2 Unit 2 • Investigation II

Check-In Are the following molecules correct according to HONC 1234? If not, what specifically is wrong with them? 1. 2. Unit 2 • Investigation II

Smells Unit – Investigation II Lesson 4: Eight is Enough

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

The Big Question How can we use Lewis dot structures to help draw structural formulas? Unit 2 • Investigation II

You will be able to: Predict whether a given compound would be stable and likely to be found in nature. Unit 2 • Investigation II

Notes Unit 2 • Investigation II

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

(cont.) Br2 H2S PH3 SiH4 (cont.) Unit 2 • Investigation II

(cont.) Unit 2 • Investigation II

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). Unit 2 • Investigation II

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

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 Unit 2 • Investigation II

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

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

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

The Big Question How do we draw a Lewis dot structure for a molecule? Unit 2 • Investigation II

You will be able to: Use Lewis dot symbols to draw a possible structure for a C2H4O2 molecule. Unit 2 • Investigation II

Notes Draw Lewis dot symbols for C and two O atoms: Bring atoms together: Create double bonds: Unit 2 • Investigation II

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

(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 Unit 2 • Investigation II

Making Sense Explain how HONC 1234 assists you in checking out the structural formulas you create. Unit 2 • Investigation II

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

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