Chapter 6...Chemistry 5th ed. 8.1-4, 8.6-7, 8.9-13, 9.1, 10.1, p. 466-474, 22.1-22.3 I. Introduction Picture1 Notice that energy As two atoms approach one another, there may be an

B O N D I N G - S T R U C T U R E C H A P T E R 5 | 1

Dena K. Leggett, Ph.D., Allen High School, Allen, TX 2012-2013

Chapter 6 CHEMICAL BONDING Zumdahl. Chemistry 5

th ed. 8.1-4, 8.6-7, 8.9-13, 9.1, 10.1, p. 466-474, 22.1-22.3

I. Introduction

Picture1

As two atoms approach one another, there may be an attraction between the electrons on one atom and the positive nucleus

on another atom. The inner, or ___________________ electrons are quite content with their attraction to their own nucleus,

but the outer, or ___________________ electrons can sometimes be kind of fickle – especially if the other nucleus is

exceedingly attractive!

Picture:2

In PreAP/IB chemistry, we focused primarily on ionic bonding and covalent bonding. We are going to expand our bonding

offerings in AP/IBHL Chemistry by including network covalent, metallic, and coordinate covalent bonding.

1 http://www.webelements.com/webelements/elements/media/nearingzero/F.gif

2 http://www.chem.ucalgary.ca/courses/351/Carey5th/Ch02/ljpot.jpg

Notice that energy when there is an attraction

between atoms to form a bond. Energy is

released when bonds form, energy is required

to break bond

After the optimal bond length –

the most stable “ r” – the energy

rapidly increases due to nucleus-

nucleus repulsion

Notice that energy when there is an attraction

between atoms to form a bond. Energy is

released when bonds form, energy is required

to break bond

After the optimal bond length –

the most stable “ r” – the energy

rapidly increases due to nucleus-

nucleus repulsion



II. Network Covalent Compounds Comic

3

A. Network covalent bonds involve the ___________________ of electrons by two atoms.

B. It differs from conventional covalent by virtue of its ___________________

___________________ , ___________________ , ___________________ of covalent

bonds between atoms arranged in a ___________________, ___________________

___________________

C. These are not ___________________ molecules with a defined beginning and end.

D. These substances are represented by the lowest whole number ratio, or

___________________ ___________________.

E. The size depends on when the ___________________ is fractured.

F. Your text discusses band-gap theory – you do not need to know this.

G. The table below outlines some common examples. The ones on the left are ___________________ of carbon.

Allotropes have the same element, but different structures and hence functions.

Name Structure Name Structure

Graphite Silica (SiO2)

SAND OR GLASS!

Diamond Silicates (SiO>2, neg

charge)

Fullerenes,

nanotubes

Silicon Carbide4

3 http://www.offthemarkcartoons.com/cartoons/1997-05-06.gif

4 http://www.nature.com/nature/journal/v430/n7003/images/430974a-f1.2.jpg

http://www.nature.com/nature/journal/v430/n7003/images/430974a-f1.2.jpg



III. METALLIC BONDING

A. Metallic bonding also involves a ___________________

___________________, ___________________, and

___________________ ___________________.

B. Metals are typically described by ___________________ electron model, sometimes called a

___________________ ___________________ ___________________.

C. Metal ions are arranged in a ___________________ and the valence electrons are ___________________

throughout the lattice structure.

D. Again, these are not ___________________ molecules with a defined beginning and end.

E. An ___________________ has a metallic ___________________ mixed with a ___________________, which is

often, but not necessarily a metal. Examples include bronze (Cu & Sn or Al) and brass (Cu & Zn).5 Alloys do not

have a constant composition and are represented by concentration units such as ppm or % by mass.

a. In ___________________ alloys, the ___________________ metal replaces the ___________________

metal at lattice points. This type of structure is common when the metal atoms are roughly the same size.

b. When the solute is smaller than the solvent, the solute molecules may squeeze into the spaces surrounding

the metal atoms. These are called ___________________ ___________________. Steel is an alloy with

carbon atoms in the interstices of an iron lattice. Stainless steel is a combination of these two types of

alloys.

c. Stainless steel is a combination of substitutional and interstitial alloy. Iron is the solvent metal, nickel and

chromium are substituted for some of the iron atoms and carbon is an interstitial solute.

5 http://en.wikipedia.org/wiki/Alloy

POSITIVE METAL ION

“SEA” (COMMUNE!) OF VALENCE ELECTRONS

http://en.wikipedia.org/wiki/Alloy



IV. Ionic Bonding A. Ionic bonds involve the ___________________ of electrons an atom of low electronegativity (likely a metal) to an

atom of high electronegativity (likely a non-metal).

B. The metal atom ___________________ electron(s) to become a ___________________ and is said to be

___________________.

C. The non-metal ___________________ electron(s) to become an ___________________ and is said to be

___________________.

Picture6

IN GENERAL: The ___________________ atoms are away from each other on the periodic table the

___________________ polar the bond. NOTE: Although carbon is more electronegative than hydrogen, a C-H bond is

considered ___________________.

Lets do it 1. Use the periodic table to predict the rank for the following bonds from least polar

(#1) to most polar(#6).

Ca-Se Li-F S-P O-F Sn-I I-O

Lets do it 2. Use electronegativity values to rank the following bonds from least polar (#1) to

most polar(#6).

Ca-Se Li-F S-P O-F Sn-I I-O

6 http://www.chemistry.ohio-state.edu/~grandinetti/teaching/Chem121/lectures/Electronegativity/ColvanttoIonic.jpg

0.5 1.0 1.5 2.0 2.5 3.0

Increasing ionic character

Increasing covalent character

At a EN = 1.7, the bond has >50% ionic

character, so we classify it as “ionic”. When in

doubt, classify it as ionic if a metal is present,

although we know from the previous example

of Sn-I that we are not always exactly correct!

0.5 1.0 1.5 2.0 2.5 3.0

Increasing ionic character

Increasing covalent character

At a EN = 1.7, the bond has >50% ionic

character, so we classify it as “ionic”. When in

doubt, classify it as ionic if a metal is present,

although we know from the previous example

of Sn-I that we are not always exactly correct!



D. Formula & structure

1. Formula units – When you write the chemical formula for an ionic compound,

you are simply indicating the smallest whole number ratio that balances charges.

2. The structure of an ionic compound is actually a long-range network of

___________________ positive and negative ions that are present in that

___________________ whole number ratio. No matter how much calcium

chloride you have, the ratio of Ca2+

to Cl─ is always 1:2.

E. Lewis Dot Structure

Step One: Form the ions. Use brackets around the ions.

·Ca·

® Caé

ëê

ù

ûú

2+

····Cl ·

··

®··

··Cl ·

···

é

ë

êê

ù

û

úú

1-

Step Two: Determine the smallest whole number ratio needed to form a neutral formula unit.

x(+2) + y(-1) = 0, least common multiple is 2, therefore two chloride ions combine with one calcium

ion Step Three: Draw the appropriate number of ions, making sure to alternate positive and negative ions.

····Cl ·

···

é

ë

êê

ù

û

úú

1-

Caé

ëê

ù

ûú

2+ ····Cl ·

···

é

ë

êê

ù

û

úú

1-

Lets do it 3. Draw Lewis dot structure for Aluminum sulfide.

F. Energy and size

1. This great little formula that can help us compare the ___________________ ___________________

between different ionic compounds, which in turn will help us compare ___________________

/___________________ in our next chapter. Note that this formula assumes that the bonds are pure

___________________ in character. Deviations from this calculation would indication increasing

___________________ character to the bond!



Cation(g) + anion(g) ionic cmpd (s)

r

QQkLE 21

Lets do it 4. You are the head chemist on the team designing the next generation of space shuttles. Your main

roadblock is developing a new, non-fossil based, fuel. You come up with the seemingly great idea of harnessing the

energy released from the formation of ionic bonds. Below are pairs you are considering. Write the lattice energy

reactions for each substance and then circle the one in each pair that should provide the greatest amount of energy

and write a sentence supporting your choice.

PAIR LATTICE ENERGY REACTIONS WINNER!

MgCl2 and NaCl

LiF and LiCl

NaCl and SrCl2

2. BORN-HABER CYCLE.7

Another way to approach the lattice energy of a substance is a more ___________________ but typically provides closer

values. In a Born-Haber cycle the lattice energy is calculated by ___________________ the energy of a variety of processes.

Although we have not had thermochemistry yet, you should be familiar with the concept of ___________________ – the

energy involved in a constant pressure process (remember exothermic and endothermic?!)

7 Pictures from http://www.4college.co.uk/a/O/bornhaber2.gif and

http://jcsu.jesus.cam.ac.uk/~rpc25/notes/chemistry/lattice_enthalpies/Image641.gif

As “r” (ie bigger ions), Lattice energy

As Q (either one!), Lattice energy

You need to know how to write the reaction equation (with phases) for lattice energy! what a lattice energy reaction is!

k = proportionality constant

Q1 = positive charge

Q2 = negative charge

R = ionic radius (distance

between ion centers)

For some reason students keep forgetting about this handy little formula! Memorize it – keep it near and dear to your heart!

http://www.4college.co.uk/a/O/bornhaber2.gif

http://jcsu.jesus.cam.ac.uk/~rpc25/notes/chemistry/lattice_enthalpies/Image641.gif





V. Covalent Compounds – INORGANIC

A. Formula & structure

1. Molecular Formulas – unlike ionic compounds, molecular formulas for covalent molecules indicate the

___________________ ___________________ ___________________ ___________________ that are

bonded to one another. They do not, however, provide much information on ___________________ the atoms are

bonded to one another. For that we need some sort of ___________________ model.

2. Structural models

a. Lewis Dot structures

Count up the total number of valence electrons

Add or subtract the appropriate number of electrons as indicated by any charge

The element with the lowest electronegativity is typically written first and is also the central

atom.

Surround the central atom with the other atoms. REMEMBER: F and H can only form one

bond, O can only form two, and B can only form three. If there is an O and an H, often the

hydrogen is bonded to the oxygen rather than the central atom.

Place 2 dots (or some other symbol!) between atoms to form bonds.

Satisfy the octet for the central atom (or the peripherals – it doesn’t matter in the end).

Attempt to satisfy the octet of peripheral atoms.

Place extra electrons on the central atom. I often draw a line to any extra non-bonded

electron pairs.

If you are short electrons, have the central atom share more electrons to form double or

triple bonds.

Draw the Lewis dot structure for CH3Cl:

Valence electrons = 4 + 3(1) + 7 = 14

Draw the Lewis Dot Structure for phosphate: Valence electrons = 5 + 4(6) + 3 = 32

Draw the Lewis Dot structure for H3PO4: Valence electrons = 3(1) + 5 + 4(6) = 32

ClH

H

H

••C••

••••ClH

H

H

C ClH

H

H

••C••

•••• ••

••••ClH

H

H

••C••

•••• ClH

H

H

••C••

••••C••

••••ClH

H

H

C ClH

H

H

••C••

•••• ••

••••ClH

H

H

••C••

•••• ClH

H

H

••C••

•••• C••

•••• ••

••••

OO

O

O

••P••

••••OO

O

O

P OO

O

O

••P••

•••• ••

••••

•• ••••

••

••••

•• ••

••

OO

O

O

••P••

•••• ••

••••

•• ••••

••

••••

•• ••

••

3-

OO

O

O

••P••

•••• OO

O

O

••P••

•••• P••

••••OO

O

O

P OO

O

O

P OO

O

O

••P••

•••• ••

••••

•• ••••

••

••••

•• ••

••

OO

O

O

••P••

•••• P••

•••• ••

••••

•• ••••

••

••••

•• ••

••

OO

O

O

••P••

•••• ••

••••

•• ••••

••

••••

•• ••

••

OO

O

O

••P••

•••• P••

•••• ••

••••

•• ••••

••

••••

•• ••

••

3-

OO

O

O

••P••

•••• OO

O

O

••P••

•••• ••

••••

•• ••••

••

••••

•• ••

••

OO

O

O

P H

H

H H

H

H H

H

H••••

••

OO

O

O

••P••

•••• OO

O

O

••P••

•••• ••

••••

•• ••••

••

••••

•• ••

••

OO

O

O

••P••

•••• P••

•••• ••

••••

•• ••••

••

••••

•• ••

••

OO

O

O

P H

H

H H

H

H H

H

H••••

••



Lets do it 5. Draw LDS for NF3, SF6, and SO42─

. Nitrogen trifluoride is used to clean chemical vapor deposition

chambers (used to deposit material on wafers). Sulfur hexafluoride is used as a dielectric (insulating material) in

high voltage circuit breakers and also as an etchant (chemically removed material) in the semiconductor industry.

Sulfuric acid is produced more than any other chemical!

Lets do it 6. Combined ionic:covalent LDS: Draw a Lewis dot structure for Sr3(PO4)2.

b. WHAT IF MORE THAN ONE LEWIS DOT STRUCTURE SEEMS REASONABLE?!!

SCENARIO ONE: The two structures are EQUAL ENERGY. Reality is a BLEND of the possibilities.

Resonance – To resonate means to match ___________________ (or vibrations). Resonance occurs when more than one

equivalent LDS structure can be drawn for a molecule. NOTE: The molecule does not transition from one resonance

structure to the next. The actual structure is best described a ___________________ or average of the resonant structures.

The shared electrons are said to be ___________________.

Bond Order=# bonds (e-pairs)

peripheral atoms sharing

Draw the Lewis Dot structure(s) for SO2

S OO •• •• •••• ••

• •• • • •

• • S OO •••• •••• ••

• •• • • •• •

or ??

S OOBond order = 1.5

S OO •• •• •••• ••

• •• • • •

• • S OO •••• •••• ••

• •• • • •• •

or ??

S OOBond order = 1.5

S OO •• •• •••• ••

• •• • • •

• • S OO •• •• •••• ••

• •• • • •

• • S OO •••• •••• ••

• •• • • •• •S OO •••• •••• ••

• •• • • •• •

or ??

S OO S OOBond order = 1.5



Picture8

NOTE: As bond order ___________________________, bond length ________________________________ & bond

energy _______________________________! (see cartoon for answers!)

Lets do it 7. Draw the LDS for the carbonate ion. What is the bond order for each bond to the carbon atom?

SCENARIO TWO: The two structures are NOT EQUAL ENERGY. Reality will be a CHOICE of the possibilities.

Formal Charge – How the heck do you know which is the most likely?? This is where formal charge comes into play.

Formal charge is a method of assigning electrons. There are two criteria to be considered:

(1) The most stable structure will typically have all formal charges as close to zero as possible

(2) If there is no choice but to have a residual negative charge, then it should be on the most electronegative atom.

FC = # valence electrons – [non-bonded electrons + ½ bonded electrons]

Lets do it 8. Use formal charges to determine the best structure for N2O

N N O Evaluation

8 http://www.newspaper.unsw.edu.au/archive/05_04_27/images/panel/images/VSU.jpg

I bet the bond

order concept is

important!

Do n ’t fo rge t th e

“s tru c tu re d e te rm in e s

fu n c tio n ” %# @** s h e

m a ke s u s kn o w !

Y eah, but its not hard!

T hink about it – as

bond order , there are

more electrons to pull

atoms closer together

so bond length

Not only that, but

increased electron

density between atoms

means the bond energy

is greater as well!...this

is scary – we are

starting to think l ike

her!

I bet the bond

order concept is

important!

Do n ’t fo rge t th e

“s tru c tu re d e te rm in e s

fu n c tio n ” %# @** s h e

m a ke s u s kn o w !

Y eah, but its not hard!

T hink about it – as

bond order , there are

more electrons to pull

atoms closer together

so bond length

Not only that, but

increased electron

density between atoms

means the bond energy

is greater as well!...this

is scary – we are

starting to think l ike

her!



c. VSEPR – this is an acronym for VALENCE SHELL ELECTRON PAIR REPULSION. The

model is built on the premise that electrons want to get as far away from one another as possible. If

you can visualize in three dimensions and apply a little geometry, this will be easy! NOTE: the order

of repulsion is:

non-bonded pair non-bonded > non-bonded pair bonded pair > bonded pair bonded pair

Cartoon9

References for visuals:

http://intro.chem.okstate.edu/1314F97/Chapter9/VSEPR.html

d. Hybridization – This model combines, or hybridizes, atomic orbitals to form molecular orbitals. For

each bond formed on the atom in question (typically the central atom or a carbon in a chain), the model

proposes hybridizing one atomic orbital. These hybridized molecular orbitals are called sigma ()

bonds. In a sigma bond, the electron density of the bond is between the atoms. The first bond

formed between two atoms is always a sigma bond. DON’T COUNT THE SECOND OR THIRD

BOND FORMED! These bonds are formed from unhybridized “p” orbitals and are called pi ()

bonds. In pi bonds, the electron density is above and below the atoms.

References for visuals:

http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/flash.mhtml

http://winter.group.shef.ac.uk/orbitron/

B + X

# MOLECULAR

ORBITALS

NEEDED

# ATOMIC ORBITALS

TO HYBRIDIZE HYBRIDIZATION

2

3

4

5

6

What is the hybridization for the sulfur in SF6? You did the LDS earlier and saw that there are six bonds to the sulfur. That means we need six atomic orbitals from S for

form the six molecular orbitals needed for SF6. That means we need: s, p, p, p, d, d atomic orbitals. We say the hybridization

is sp3d

2 (NOTE: some sources would write this as d

2sp

3)

9 http://comosr.spps.org/sites/93f37ca8-07e5-4006-a522-

e7a5c43def17/uploads/Edited_Cartoon_male_teacher_using_overhead.JPG

We’re going to do a modeling activity that incorporates all of these models. THIS IS VERY IMPORTANT! I don’t know about you, but I have trouble thinking in 3-D, so we are going to play with models. If you understand this chart, you will be well on your way to correctly answering many of the anal questions we chemists contrive!

http://intro.chem.okstate.edu/1314F97/Chapter9/VSEPR.html

http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/flash.mhtml

http://winter.group.shef.ac.uk/orbitron/



What is the hybridization on the carbon in H2CO(formic acid – the sting of an ant bite That means we need s, p, & p or a hybridization of sp

2

Check out this website to see rotating molecules! http://www.molecules.org/VSEPR_table.html

In order to simplify the memorization, we are going to use the following notation to generalize molecule types:

A = central atom B = # peripheral atoms X = # non-bonded electron pairs

Use this notation to memorize the names of the shapes!

Polarity – the word polarity implies some sort of an opposition or separation. We talk about two people being “polar

opposites.” Magnets and the earth both have north/south poles.10

Politics and religion can be VERY POLARIZING topics!

In our context, we are going to be looking at the separation of charge that arises when there is an ___________________

electron distribution within a molecule. This permanent, uneven charge distribution is called a ___________________

dipole moment.

Molecules with a permanent dipole moment (ie polar molecules)

will line up when placed in an electric field. NOTE: positive with

negative and vice versa!)

10

http://www.physics.ubc.ca/~outreach/phys420/p420_01/shaun/shaun/whyit7.jpg

In the CH3Cl molecule, EN(Cl) > EN (H & C). This means the electrons have a greater probability of being found in the region of space nearer the chlorine so that end of the molecule has a partial negative charge, leaving the other end electron deficient and partially positive. CH3Cl has a permanent dipole moment.

In H2O, EN(O) > EN (H) & there a two non-bonding pairs of electrons. Electron density on oxygen end > hydrogen end, so oxygen end has partial negative and hydrogen end has partial positive charge. Water has a permanent dipole moment. The arrow indicates the DM.

In CO2, EN(O) > EN (C) BUT oxygens pull evenly on both sides – no uneven distribution of electron density, no permanent dipole moment

In CCl4, EN(Cl) > EN (C) BUT chlorines pull evenly on all sides – no uneven distribution of electron density, no permanent dipole moment

http://www.molecules.org/VSEPR_table.html



BUT DR. LEGGETT – WHAT ABOUT THOSE DOUBLE AND TRIPLE

BONDS WE HAVE BEEN IGNORING?

The first bond formed between two atoms is called a ___________________ () bond. The electron

density in this type of bond is centered ___________________ the atoms.

The second and third bonds formed are called ___________________ () bonds. The bond is formed

between valence electrons in non-hybridized “p” orbitals. The electron density is centered either ___________________

/___________________ OR ___________________ /___________________ of the bonding atoms.

Lets do it 9. Let’s evaluate theobromine, a key component in chocolate! Step one: Draw in “C” atoms at each “bend”.

Step two: Count all the bonds to the carbon atoms – there must be four. If there aren’t – add “H” atoms! Step

three: Count the number of sigma and pi bonds. BE CAREFUL – “CH3” represents three sigma bonds. Step four:

Add non-bonded pairs of electrons to nitrogen and oxygen so that each has an octet. Step five: indicate the

hybridization around the oxygen, nitrogen and carbon atoms.

VI. Covalent Molecules – ORGANIC

This is a HUGE area of chemistry. We are only going to learn basic naming and ___________________

groups.

CLASS FUNCTIONAL

GROUP

NAMING EXAMPLE FUNCTIONAL

GROUP

POLARITY

MLCL

FORMULA

Alkane

Alkene

Alkyne



Alcohol

Aldehyde

Ketone

Carboxylic

Acid

Amine

VII. Coordinate Covalent Bonding

A. Definitions:

a. Coordinate Covalent Bond: A covalent bond in which ___________________ of the bond participants

supplies ___________________ of the electrons.11

b. Complex ion:

i. A metal ion, an ion such as H+, or an electron deficient atom acts as a ___________________

___________________ and ___________________ electron pairs.

ii. Ligand: group with non-bonded pair of electrons that can ace as a ___________________

___________________ (donates electron pairs)

c. Coordination complex: Complex ion with a counter ion to balance charge to form a neutral complex

d. Coordination number: The number of bonds a metal ion is able to form with ligands. Depends on

size, oxidation state and electron configuration.

B. Common Coordination numbers

2 2 & 4 4 4 & 6 6 Ag

+ Cu+ Zn

2+ Al3+ Fe

3+

Au+ Cd

2+ Co2+ Fe

2+

Ni2+ Cr

3+

Cu2+ Co

3+

11

http://hrsbstaff.ednet.ns.ca/dawsonrj/12%20Chem/Chapter%20notes/Chapter%2019%20%20Notes_files/image006.gif

NOTE: AP will accept any reasonable coordination

number. For most of these it means that you can use a

coordination number that is simply twice the oxidation

number! Fe2+

is the only exception.

http://hrsbstaff.ednet.ns.ca/dawsonrj/12%20Chem/Chapter%20notes/Chapter%2019%20%20Notes_files/image006.gif



C. Common Ligands:

Ligand Name Charge balance

CN− Cyano must balance + and – charge I

− Iodo must balance + and – charge

OH− Hydroxo must balance + and – charge SCN

− thiocyano must balance + and – charge

F−

Fluoro must balance + and – charge

Cl− Chloro must balance + and – charge NH3 Ammine charge is the same as the + ion

Br− Bromo must balance + and – charge H2O Aqua charge is the same as the + ion

D. Structures12

VII. Sample AP Questions: Copyright College Board – for face to face teaching only

1997 - Consider the molecules PF3 and PF5.

a) Draw the Lewis electron-dot structures for PF3 and PF5 and predict the molecular geometry of each.

b) Is the PF3 molecule polar, or is it nonpolar? Explain.

c) On the basis of bonding principles, predict whether each of the following compounds exists. In each

case, explain your prediction.

(i) NF5

(ii) AsF5

12

http://www.chemguide.co.uk/inorganic/complexions/octions.gif

http://www.chemguide.co.uk/inorganic/complexions/octions.gif



1992 D

NO2 NO2─ NO2

+

Nitrogen is the central atom in each of the species given above.

(a) Draw the Lewis electron-dot structure for each of the three species.

(b) List the species in order of increasing bond angle. Justify your answer.

(c) Select one of the species and give the hybridization of the nitrogen atom in it.

(d) Identify the only one of the species that dimerizes and explain what causes it to do so.

Documents

Chapter 6...Chemistry 5th ed. 8.1-4, 8.6-7, 8.9-13, 9.1, 10.1, p. 466-474, 22.1-22.3 I. Introduction Picture1 Notice that energy As two atoms approach one another, there may be an