COVALENT BONDING
Mr. O’Brien (SFHS)
Chapter 9
Standard 2A.B.E.
Formation & Properties of
COVALENT BONDS (std.2A&B)
What are covalent bonds composed of?
– Bonds between non-metal elements.
– Primarily: Carbon, Oxygen, Hydrogen, and Nitrogen.
How are covalent bonds formed?
– By the sharing of valence electrons
– Non-metal atoms have similar electronegativity (attraction
to electrons)
Covalent solids are known as molecules.
– Monatomic Molecule
– Diatomic Molecules
– Other Biological Molecules
Biological Molecules
Checking for Understanding
Identify the following elements as
ionic, metallic or covalent.
H2O Steel Mg(NO3)2 CO2 NH4Cl
Do you think covalent bonds form
ions? Explain your reasoning.
Formation & Properties of
COVALENT BONDS (std.2A&B)
What are properties of Covalent bonding?
– Mostly soft solids
– Low melting/boiling points
• Many covalent molecules exist as gas!
– Nonconductor
(diagram 1) Example of
covalent compounds existing as
gas. Carbon Monoxide, CO.
Checking for Understanding
Account for the weakness in covalent bonds.
Hint: think about what it doesn’t have that ionic/metallic have
(diagram 2) Example of
Important Point
(diagram 3) Example of
covalent compounds existing as
weak solids. Polyethylene, C2H4.
covalent compounds existing as
weak solids. Melting butter..
Because Biological Molecules are covalently bonded,
they can be easily broken down by the body.
Formation & Properties of
COVALENT BONDS (std.2A&B)
Key Terms
Nonpolar-Covalent
(molecules EQUALLY share valence electrons)
PRETEND for a moment that you were to
share a pizza with a friend
How much would you share?
Polarity explains
equal or unequal
sharing between atoms.
Polar-Covalent
(molecules UNEQUALLY share valence electrons)
How can you tell the polarity?
Checking for Understanding
What does the drawing indicate about
the sharing of ve that is occurring
(polarity)?
Formation & Properties of
COVALENT BONDS (std.2A&B)
Honors
Electronegativity Differences
Between Covalent & Ionic Bonds
0-0.3
Nonpolar-Covalent
0.4 – 1.9
Polar-Covalent
2.0 +
Ionic
Checking for Understanding
Distinguish between nonpolar or polar
covalent, and ionic bonds.
C-H H-O Na-S
H-H C-Cl
How are polar-covalent bonds similar to ionic bonds?
Both contain charges!
δ- indicate slight negative charge.
δ+ indicate slight positive charge.
Drawing Lewis Dot Structures (std.2E)
How to draw Lewis Dot Structures for Covalent Bonds?
1. Count the TOTAL number of valence electrons in
the molecule
2. Write the symbol for atom in the formula. Start
forming octets around each atom by placing the
electrons you counted.
(Except for Hydrogen)
•
3.
Important Terms
LONE Pairs
electrons not involved in bonding
You can only use the TOTAL number of valence
electrons you found!
SHARING Pairs
2 electrons that are being
shared/bonded
represented with “—”
If not enough valence electrons to make octets,
START SHARING between the atoms.
–
Move lone pair in between atoms to share.
Checking for Understanding
Draw the Lewis Dot Structure for each Non-polar molecule
F2
O2
N2
CH4
HF
Drawing Lewis Dot Structures
(std.2E)
• What is the “HONC” rule?
– The following elements
must have:
 H (1 bond)
 O (2 bonds)
 N( 3 bonds)
 C (4 bonds)
• Use the HONC rule to
check your
drawings!
Checking for Understanding
Draw the Lewis Dot Structure for
Each polar molecule
H2O
NH3
HCN