Chapter 9: Covalent Bonds
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What is a Covalent Bond?
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Covalent Bond -The result of sharing
valence electrons. The shared electrons
are part of the complete outer shell of
both atoms.
• Occurs when elements are close together on
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the periodic table
Between nonmetallic elements
Molecule-formed when two or more
atoms bond covalently.
Covalent Bonds
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Can exist as gases, liquids, or solids
depending on molecular mass or polarity
Usually have lower MP and BP than
ionic compounds
Do not usually dissolve in water
Do not conduct electricity
Types of Bonds:
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Nonpolar covalent (also called pure covalent)
– equal sharing of electrons between atoms;
example: O2
Polar covalent – unequal sharing of electrons
between atoms; example: H2O
Ionic – complete transfer of electrons;
example: NaCl
*electronegativity (EN) – indicates how strongly
an atom wants to gain an electron
Diatomic Molecules
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Contains only two atoms. 7 naturally
occurring in nature
•H
•O
•F
• Br
•I
•N
• Cl
H2
O2
F2
Br2
I2
N2
Cl2
TO PREDICT BOND TYPE:
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Look at table of EN values and subtract
the values for the 2 atoms involved in the
bond
take the absolute value
If EN difference is…
0 – 0.4  nonpolar covalent bond
0.5 – 1.6  polar covalent bond
>1.7  ionic bond
TO DETERMINE MOLECULAR
SHAPE
Use VSEPR (valence shell electron pair
repulsion) rules:
1) Draw the Lewis dot structure for the molecule
2) Identify the central atom
3) Count total # of electron pairs around the central
atom
4) Count # of bonding pairs of electrons around the
central atom
5) Count # of lone pairs of electrons around the
central atom
6) Look at summary chart, identify shape
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Practice:
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Determine the shape.
1. BCl3
2. CaO
Polarity
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TO DETERMINE THE POLARITY OF
A MOLECULE, not a bond, you must
know the type of bond and the shape.
POLAR MOLECULES must meet 2
criteria:
Must have a polar covalent bond (EN
difference between 0.5 and 1.6) AND
Determining Polarity
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Must have an asymmetrical shape:
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If both criteria are not met, it is not a
polar molecule, it is either a nonpolar
molecule or an ionic compound.
• trigonal pyramidal or
• angular, or
• 2 element linear
Practice:
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Label the following MOLECULES as
polar or nonpolar.
1. NH3
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2. CH4
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3. HCl
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Practice:
What type of bond that will occur
between each of the following?
 1. BCl3
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2. CaO
Lewis Structures for Molecules
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Single Covalent Bonds
• Hyrdrogen + Bromine
• Carbon + Chlorine
Naming Molecules
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Binary molecules-Rules
1. Name the first element using the entire
name
2. The second element is named using the root
and the suffix (ending) –ide
3. Prefixes are used to indicate the number of
each type of atom. (Table 9-1)
Exception-the first element will never have the
prefix mono
TO DETERMINE STATE OF
MATTER:
1. Determine if compound is ionic, polar,
or nonpolar.
2. Calculate molar mass of compound by
adding the mass of each of the
elements in the compound.
3. Look at the state of matter chart.
Practice:
What is the state of matter of the
following compounds?
1. HBr
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2. NH3
3. CaCl2
Chapter Review Quiz
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Take the online review quiz from the
textbook to get an idea of how you might
perform on the multiple choice portion of
the test.
If you scored less than 14 of 20 correct
70% you need to spend more time
studying.