Unit 6: Covalent Bonding &
Nomenclature
Section 1: Covalent Bonding & Lewis
Structures
These toy models
are made from circular
pieces joined together
in units by sticks.
Atoms can also be
arranged in different
ways to make a variety
of products.
8.1
covalent bond – formed by sharing e-’s
between atoms. (nonmetals only)
molecule – neutral group of atoms
joined by covalent bonds.
molecular compound – composed of
molecules with covalent bonds.
8.1
diatomic molecule – molecule consisting
of two atoms of the same element.
Memorize these!!
8.1
molecular formula: shows how many atoms
of each element a molecule contains.
8.1
Properties of molecular compounds:
 lower melting and boiling points than
ionic compounds. (usually liquid or gas)
 poor conductors
8.2
Octet Rule:
atoms tend to combine to have 8 electrons in
their outer shell like noble gases.
8.2
lone pair
unshared pair
nonbonded pair
1 shared pair
single bond: atoms
bonded by sharing
a pair of electrons.
8.2Covalent Bonds
Single
How many unshared pairs?
8.2
Single Covalent Bonds
How many shared pairs?
8.2
Double and Triple Covalent Bonds
double bond: bond that shares two pairs
of electrons.
O
O
triple bond: bond that shares three pairs
of electrons.
N
N
8.2
HONORS
Super Special Carbon
Carbon can form long chains
because it forms up to 4 bonds
on each carbon atom.
Without this property, large
biomolecules could not form
such as:
proteins
lipids (fats)
carbohydrates (sugars/starches)
nucleic acids (DNA/RNA)
Writing Lewis Structures
PCl3
5 + 3(7) = 26
1. Add valence electrons
of all atoms.
Writing Lewis Structures
2. Central atom is
the least
electronegative.
(to the left in PT)
Connect all single
bonds.
Keep track of the electrons:
26  6 = 20
Writing Lewis Structures
3. Fill the octets of
the outer atoms.
Keep track of the electrons:
26  6 = 20  18 = 2
Writing Lewis Structures
4. Fill the octet of
the central atom.
Keep track of the electrons:
26  6 = 20  18 = 2  2 = 0
Writing Lewis Structures
5. If you run out of
electrons before the
central atom has an
octet…
…form multiple
bonds until it does.
8.1
Section Assessment
Draw the Lewis structure for trichloromethane,
CHCl3
Draw the Lewis structure for carbon dioxide,
CO2
O
C
O
Quick Quiz!
1. A molecular compound usually consists of
A. two metal atoms and a nonmetal atom.
B. two nonmetal atoms and a metal atom.
C. two or more metal atoms.
D. two or more nonmetal atoms.
Quick Quiz.
2. A molecular formula shows
A. how many atoms of each element a molecule
contains.
B. a molecule's structure.
C. which atoms are bonded together.
D. how atoms are arranged in space.
Quick Quiz.
3. Compared to ionic compounds, molecular
compounds tend to have relatively
A. low melting points and high boiling points.
B. low melting points and low boiling points.
C. high melting points and high boiling points.
D. high melting points and low boiling points.
Quick Quiz.
4. In covalent bonding, atoms attain an octet
electron configuration like noble gases by
A. losing electrons.
B. gaining electrons.
C. transferring electrons.
D. sharing electrons.
Quick Quiz.
5. Carbon atoms have 4 valence electrons to
form up to 4 bonds. This allows carbon to
form _________________ needed for life.
A. large, long chain biomolecules.
B. nucleic acids
C. carbohydrates
D. all of the above
Quick Quiz.
6. Which of the following diatomic molecules
have a triple bond?
(hint: draw the Lewis structures)
A. O2
O
O
B. N2
N
N
C. Br2
Br
Br
D. H2
H
H
Quick Quiz.
7. Draw the correct Lewis structure for nitrous
oxide (or laughing gas), N2O.
hint: arrange the atoms as…
N
N O
N
N O