smells unit investigation 5: picturing molecules lesson 2: honk if you like molecules lesson 3:...

Smells Unit

Investigation 5: Picturing Molecules

Lesson 2: Honk If You Like MoleculesLesson 3: Connect the Dots

Lesson 4: Eight is EnoughLesson 5: Dots, Dots, and More Dots

Smells Unit – Investigation II

Lesson 3:

Connect the Dots

© 2004 Key Curriculum Press.

Unit 2 • Investigation II

ChemCatalyst

• This is a drawing of the structural formula of a methane molecule. The lines represent bonds. Explain what you think a bond is.

C H

H

H

H



The Big Question

• How can Lewis dot symbols help us to understand and predict bonding?



You will be able to:

• Draw the Lewis dot symbol for an element and predict how many covalent bonds it will make.



• A covalent bond is a connection that forms between two atoms when those atoms are sharing a pair of electrons between them.

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.

Notes (cont.)

(cont.)



• Nitrogen, with 5 valence electrons, would be drawn as follows:

N N N N Nstart here

• 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.

Notes (cont.)

N N N N Nstart here



C H

H

H

H

CH

H

H

H

CH H

H

H

CH

H

H

H

Notes (cont.)



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.)



C N O F Ne

Si P S Cl Ar



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.)

(cont.)



CH4 + CH

H

H

H

NH3 +

OH2 +

(cont.)



Making Sense

• Based on what you’ve learned in this lesson, explain why the HONC 1234 rule works.



C HON

CH O N

Notes



• 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

N H

H

H

lone pair of electrons

bonded pair of electrons

Notes (cont.)



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?



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.


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?

C C C N C C C

CH

H

H

H

H H

H

H

H

H H

H H

HH

HC

H

H H

diisobutylamine

C

C C

C

CC

CC

C

C

O

HH

H

H

H

HH

HH

HH

HH

H

HH

H

menthone

H



The Big Question

• How can HONC 1234 help us to draw structural formulas?




• Determine whether the structural formula of a given molecule is possible.



• 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

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.

Notes (cont.)



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.



Molecular formula #1 — C3H8

Molecular formula #2 — C3H8O

Molecular formula #3 — C3H9N



Making Sense

• The third molecular formula has at least three possible structures.

• Are these all the same molecule? Explain.



Molecular formula #1 (the same molecule drawn with 2 different orientations)

H

H

C CC

HH

HH

H

H

H

H

C

C

C

H

H

H

H

H

H

(cont.)

Notes



Molecular formula #2 (4 different drawings are shown – 3 different molecules are represented)

H

H

C CC

HH

HH

H

H

OH

H

C CC

H

H

HH

H

HO

O

H

H

C CC

HH

H

H

H

H

H

CC

HH

H

H

H

O C

H

H

(cont.)

Notes (cont.)



Molecular formula #3 (4 different drawings are shown – but they represent only 3 different structures)

H

C CC

HH

HH

H

H

N

H

H

H

C CC

HH

HH

H

H

N

H

H

H

C CC

H

H

HH

H

H

N

H

H

H

C CC

HH

H

H

H

N H

H

H

(cont.)

Notes (cont.)



• Molecules are isomers of one another if they have the same molecular formula but different structural formulas

Notes (cont.)



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)


Double Check Your Understanding

Go back to Connect the Dots and answer

1. Making Sense

2. Homework Question 2




Check-In• Are the following molecules correct according

to HONC 1234?

• If not, what specifically is wrong with them?

1. 2.H

C

H

H O H C

H

H

H

C

H

O

H

H

C

H

H


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



The Big Question

• How can we use Lewis dot structures to help draw structural formulas?




• Predict whether a given compound would be stable and likely to be found in nature.



Cl Cl+ Cl Cl

Notes



ActivityPurpose: 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.



Br2 H2S PH3 SiH4

(cont.)

(cont.)



CCl4 C+

Cl

Cl

Cl

Cl

P F+ 3 P

F

FF

P F

F

F

(cont.)



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).



• 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

Notes



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



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.


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.

N N O O F F



The Big Question

• How do we draw a Lewis dot structure for a molecule?




• Use Lewis dot symbols to draw a possible structure for a C2H4O2 molecule.



Draw Lewis dot symbols for C and two O atoms:

Bring atoms together:

Create double bonds:

C O Oand and

CO O

CO O

Notes



ActivityPurpose: 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.



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

(cont.)



Making Sense

• Explain how HONC 1234 assists you in checking out the structural formulas you create.



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)



Wrap-Up

• Atoms can form double and triple bonds to satisfy the octet rule

smells unit investigation 5: picturing molecules lesson 2: honk if you like molecules lesson 3:...

Documents

key curriculum press

smells unit investigation

ar slide

valence electrons

unpaired electrons

dots lesson

electron pair

lewis dot symbols