Chapter 8 – Covalent Bonding
Mr. Calmer
Lawndale High School
Review of Chapter 7
In Chapter 7, we learned about electrons being
transferred (“given up” or “stolen away”)
This type of “tug of war” between a METAL
and NONMETAL is called an IONIC BOND,
which results in a SALT being formed
Chapter 8.1 – Molecular Compounds
In this chapter, you will learn about another
type of bond in which electrons are shared
Covalent Bonds are atoms held together by
SHARING electrons between NONMETALS
Salt versus Molecules
A metal cation and nonmetal anion are joined
together by an ionic bond called SALT
A group of atoms joined together by a
covalent bond is called a MOLECULE
Monatomic vs. Diatomic Molecules
Most molecules can be monatomic or diatomic
Diatomic Molecule is a molecule consisting
of two atoms
There are 7 diatomic molecules (SUPER 7) –
N2, O2, F2, Cl2, Br2, I2, H2
Properties of Molecular Compounds
Liquids or gases at room temperature
Lower Melting Points than Ionic Compounds
(which means that they are weaker than ionic)
Check in
Write a 5 word sentence describing
molecules
Make a venn diagram for monoatomic vs
diatomic molecules
Molecular Formulas
The Molecular Formula is the formula of a
molecular compound
It shows how many atoms of each element a
molecule contains
Example
H2O
contains 3 atoms (2 atoms of H, 1 atom of O)
C2H6 contains 8 atoms (2 atoms of C, 6 atoms of H)
Practice
How many atoms total and of each do the
following molecular compounds contain?
1. H2
2. CO
3. CO2
4. NH3
5. C2H6O
Practice: True or False
1. All molecular compounds are composed of
2.
3.
4.
5.
atoms of two of more elements.
All compounds are molecules.
Molecular compounds are composed of
two or more nonmetals.
Atoms in molecular compounds exchange
electrons.
Molecular compounds have higher melting
and boiling points than ionic compounds.
Ionic versus Covalent
IONIC
COVALENT
Bonded Name
Salt
Molecule
Bonding Type
Transfer e-
Share e-
Types of Elements
Metal & Nonmetal
Nonmetals
Physical State
Solid
Solid, Liquid, or Gas
Melting Point
High (above 300ºC)
Low (below 300 ºC)
Solubility
Dissolves in Water
Varies
Conductivity
Good
Poor
Check in
Make a Venn Diagram from ionic vs
covalent bonds
Chapter 8.2 – Covalent Bonding
Remember that ionic compounds transfer
electrons in order to attain a noble gas
electron configuration
Covalent compounds form by sharing
electrons to attain a noble gas electron
configuration
Regardless of the type of bond, the Octet Rule
still must be obeyed (8 valence electrons)
Single Covalent Bond
A Single Covalent Bond consists of two atoms
held together by sharing 1 pair of electrons (2 e-)
Electron Dot Structure
Shared versus Unshared Electrons
A Shared Pair is a pair of valence electrons
that is shared between atoms
An Unshared Pair is a pair of valence
electrons that is not shared between atoms
Check in
What was the difference between the
pictures
Make a guess and tell your neighbor
Practice Lewis Dot Structures
Chemical
Formula
F2
H2O
NH3
CH4
# of
Valence
Electrons
Single Line
Bond
Structure
# of
Remaining
Electrons
Lewis Dot
Structure
Octet Check
All Atoms=8
Hydrogen=2
Double Covalent Bonds
Sometimes atoms attain noble gas configuration
by sharing 2 or 3 pairs of electrons
A Double Covalent Bond is a bond that
involves 2 shared pairs of electrons (4 e-)
Triple Covalent Bond
A Triple Covalent Bond is a bond that
involves 3 shared pairs of electrons (6 e-)
Covalent Bonds
Practice Lewis Dot Structure
Chemical
Formula
O2
CO2
N2
HCN
# of
Valence
Electrons
Single Line
Bond
Structure
# of
Remaining
Electrons
Lewis Dot
Structure
Octet Check
All Atoms=8
Hydrogen=2
Bond Dissociation Energy
Bond Dissociation Energy is the energy
required to break a bond between two atoms

A large bond dissociation energy corresponds
to a strong bond which makes it unreactive

Carbon has strong bonds, which makes carbon
compounds stable and unreactive
Chapter 8.3 - Bonding Theories
So far, the orbitals we have been discussing
are atomic orbitals (s, p, d, f) for each atom
When two atoms combine, their atomic orbitals
overlap and they make molecular orbitals
A Molecular Orbitals is an orbital that
applies to the entire molecule, instead of
just one atom
Molecular Orbitals

Just as atomic orbitals belong to a particular
atom, a molecular orbital belongs to
molecules as a whole
Each orbital is filled with 2 electrons
 A Bonding
Orbital is an orbital that can be
occupied by two electrons of a covalent bond
(it’s the space in between the two atoms)
There are 2 types of bonding orbitals:
sigma and pi
Sigma Bond ()
A Sigma Bond is when 2 atomic orbitals
combine to form a molecular orbital that is
symmetrical around the axis
S orbitals overlapping
P orbitals overlapping end-to-end
Pi Bond ()
Pi bonding electrons are likely to be found
in a sausage-shape above and below the axis
 Pi bonds are weaker than sigma bonds
because they overlap less
P orbitals overlapping
side-by-side
VSEPR Theory
VSEPR Theory predicts the 3D shape of
molecules

According to VSEPR, the repulsion of
electrons causes the shape of the
molecule to adjust so that the electrons are
far apart
Valence
Shell Electron Pair
Repulsion
A Few VSEPR Shapes
Nine possible molecular shapes
Practice drawing
VSEPR Theory


Unshared pairs of electrons are very
important in predicting the shapes of
molecules

Each bond (single, double, or triple) or
unshared pair is considered a steric number

Use the steric number to predict the
molecular geometry
VSEPR can only be used with the central atom
Practice
Methane (CH4) – tetrahedral
Ammonia (NH3) – pyramidal
Water (H2O) – bent
Carbon Dioxide (CO2) - linear
Hybrid Orbitals
VSEPR is good at describing the molecular
shapes, but not the types of bonds formed
Orbital hybridization provides information
about both molecular bonding and
molecular shape

In hybridization, several atomic orbitals
mix to form hybrid orbitals
Bond Hybridization
Hybridization Involving Single Bonds – sp3 orbital

Ethane (C2H6)
Hybridization Involving Double Bonds – sp2 orbital

Ethene (C2H4)
Hybridization Involving Triple Bonds – sp orbital

Ethyne (C2H2)
Try Drawing them
https://www.khanacademy.org/science/orga
nic-chemistry/gen-chemreview/hybridization/v/pi-bonds-and-sp2hybridized-orbitals
Chapter 8.4 – Polar Bonds and Molecules
There are two types of covalent bonds
 Nonpolar Covalent Bonds (share equally)
 Polar Covalent Bonds (share unequally)
Polar Covalent
• A Polar Covalent Bond is unequal sharing of
electrons between two atoms (HCl)
• In a polar covalent bond, one atom typically has a
negative charge, and the other atom has a positive charge
Nonpolar Covalent Bond
•
A Nonpolar Covalent Bond is equal sharing of
electrons between two atoms (Cl2, N2, O2)
Classification of Bonds
You can determine the type of bond between two
atoms by calculating the difference in
electronegativity values between the elements
Type of Bond
Nonpolar Covalent
Electronegativity
Difference
0  0.4
Polar Covalent
0.5  1.9
Ionic
2.0  4.0
Practice
What type of bond is HCl? (H = 2.1, Cl = 3.1)
Difference = 3.1 – 2.1 = 1.0
Therefore it is polar covalent bond.
Your Turn To Practice

N(3.0) and H(2.1)

H(2.1) and H(2.1)

Ca(1.0) and

Al(1.5) and Cl(3.0)

Mg(1.2) and
O(3.5)
Dipole
• No bond is purely ionic or covalent …
they have a little bit of both characters
When there is unequal sharing of electrons a
dipole exists
Dipole is a molecule that
has two poles or regions
with opposite charges
A
dipole is represented
by a dipole arrow
pointing towards the
more negative end
Practice Drawing Dipoles
P- Br
P = 2.1
Br = 2.8
P –Br
+
Practice
H(2.1) – S(2.5)
 F(4.0) - C(2.5)
 C(2.5) - Si(1.8)
 N(3.0) – O(3.5)

-
Attractions Between Molecules
Besides ionic, metallic, and covalent bonds,
there are also attractions between molecules
Intermolecular attractions are weaker than
ionic, covalent, and metallic bonds
There are 2 main types of attractions between
molecules: Van der Waals and Hydrogen
Van der Waals Forces
Van der Waals forces consists of the two
weak attractions between molecules
1. dipole
interactions –
polar molecules
attracted to one
another
2. dispersion
forces –
caused by
the motion
of electrons
(weakest of
all forces)
Hydrogen Bond

Hydrogen Bonds are forces where a
hydrogen atom is weakly attracted to an
unshared electron pair of another atom
Hydrogen Bond

This other atom may be in the same
molecule or in a nearby molecule, but
always has to include hydrogen
Hydrogen Bonds have about 5% of the
strength of an average covalent bond
 Hydrogen Bond is the strongest of all
intermolecular forces

Intermolecular Attractions

A few solids that consist of molecules do
not melt until the temperature reaches
1000ºC or higher called network solids
(Example: diamond, silicon carbide)

A Network Solid contains atoms that are
all covalently bonded to each other
• Melting a network solid would require breaking
bonds throughout the solid (which is difficult to do)
Homework
Chapter 8 Assessment Page 247
#’s 39-41, 43-46, 51, 53, 54, 57-59, 61, 65, 68,
83, 85, 86, 89, 96, 99, 100