CHAPTER 6:
COVALENT COMPOUNDS
Section 1: Covalent Bond
Section 2: Drawing and Naming
Section 3: Molecular Shapes
Chapter 6
Section 1 Covalent Bonds
Objectives
• Explain the role and location of electrons in a
covalent bond.
• Describe the change in energy and stability that
takes place as a covalent bond forms.
• Distinguish between nonpolar and polar covalent
bonds based on electronegativity differences.
• Compare the physical properties of substances that
have different bond types, and relate bond types to
electronegativity differences.
Covalent bond = Sharing electrons
A covalent bond is a bond formed when atoms share
one or more pairs of electrons.
non-metals and non-metals or hydrogen and nonmetals.
and halogens
They share electrons so that both of them can have a
stable octet.
Covalent bond animation
 Formation of a Covalent Bond
A molecular orbital is the region of high probability that is
occupied by an individual electron as it travels with a
wavelike motion in the 3D space around one of two or more
associated nuclei.
Section 1 Covalent Bonds
Energy and Stability
Energy Is Released When Atoms Form a Covalent Bond
Molecule is more stable =
less energy PE=0
(like the ball at the bottom of
the hill)
Bond length: distance from one nucleus to the other that gives
lowest PE (balance between repulsive force of nuclei, and
being separate atoms)
Bond information
 Bonds are flexible: vibrate and rotate
 Bond energy: they have different strengths.
(shorter bond length = stronger bond)
 Bond strength: single<double<triple
 Electronegativity - The ability of an atom to attract
electrons in another atom
• The difference in electronegativity (
)
between two atoms in a bond to determine
how the electrons are shared or not.
Chapter 6
Predicting Bond Character from
Electronegativity Differences
There are two types of covalent bonding.
In a bond atoms can share the electrons:
1. Sharing equally = Non-polar bonding
2. Sharing unequally = Polar bonding
The number of shared electrons depends on the
number of electrons needed to complete the octet.
Ionic vs. Covalent
Nonpolar covalent bond (pure covalent) - a
weak covalent bond in which the bonding (valence)
electrons are shared equally (
< 0.5)
Polar covalent bond - a medium-strength
covalent bond in which the bonding electrons are
not shared equally
(
generally between 0.5 and 2.1)
Ionic bond - a strong bond created by the strong
electrostatic attraction of + ions and - ions. Electrons
have been given up by the cation and taken by the
anion.
(
generally greater than 2.1)
Electronegativity difference =
Calculate how electrons are shared using
Electronegativity.
0
0.5
2.1
ionic
3.3
Practice: Order the following bonds according
to increasing polarity:
H--H, O--H, F--H, S--H, Cl--H
Chapter 6
Section 1 Covalent Bonds
1. Greater electronegativity differences tend to cause
stronger bonds.
2. Stronger bonds generally have shorter bond lengths.
Chapter 6
Section 1 Covalent Bonds
Polarity Is Related to Bond Strength
• In general, the greater the electronegativity
difference, the greater the polarity and the stronger
the bond.
NON-POLAR BONDING results when two identical nonmetals equally share electrons between them.
POLAR BONDING results when two different non-metals unequally
share electrons between them.
Every PB has a
Dipole.
One end of the bond is more
negative (higher EN) and the
other end is positive (lower EN).
(delta) is the sign

for the more negative end

for the more positive end
Example:
Hydrogen bonded to Oxygen
EN=2.1
EN=3.5
Physical Properties and Polarity
 Covalent compounds (non-polar and polar), molecules with
more polarity are more attracted to each other and thus have
higher melting and boiling points.
 Solubility: like dissolves like
Polar dissolves polar and ionic (water and salt, water and
sugar)
Non-polar dissolves non-polar (Oil dissolves fats)
Oil and water don’t mix!
Chapter 6
Properties of Substances with Metallic,
Ionic, and Covalent Bonds
Group activity
group of two (discuss together and answer)
Complete each statement below by choosing a term from the
following list. Terms may be used more than once.
Energy
Polar covalent
electronegativity
nonpolar covalent
dipole
length
1.
Bond ___________ is defined as the average distance between two
bonded atoms at their minimum PE.
2.
Bond ________ is defined as the energy required to break the
chemical bond between two atoms and separate them.
3.
A ________ bond is an attraction between two atoms in which
bonding electrons are shared equally between the atoms.
4.
A ________ bond is an attraction between two atoms in which
bonding electrons are localized on the more EN atom.
5.
A _________ molecule is one that has a partial positive charge at
one end and partial negative charge at the opposite end.