Chemistry Reference
In-Depth Information
O
C
O
C
O
O
2 oxygen atoms
carbon atom
carbon dioxide molecule (CO
2
)
Figure 3.28
Formation of carbon dioxide.
C
a
Carbon dioxide molecule. Note the double covalent bond is
represented by a double line.
O
O
Covalent structures
Compounds containing covalent bonds have
molecules whose structures can be classifi ed as either
simple molecular
or
giant molecular
.
Simple molecular structures are simple, formed
from only a few atoms. They have strong covalent
bonds between the atoms within a molecule
(
intramolecular bonds
) but have weak bonds
between the molecules (
intermolecular bonds
).
Some of the strongest of these weak intermolecular
forces occur between water molecules.
One type of weak bond between molecules is
known as the
van der Waals' bond
(or force), and
these forces increase steadily with the increasing
size of the molecule.
b
Model of the linear carbon dioxide molecule.
Figure 3.29
Examples of simple molecules are iodine
(Figure 3.30), methane, water and ethanol.
Questions
1
Draw diagrams to represent the bonding in each of the
following covalent compounds:
a
tetrachloromethane (CCl
4
)
weak intermolecular bond
I
e
ethene (C
2
H
4
)
b
oxygen gas (O
2
)
f
methanol (CH
3
OH)
I
I
c
hydrogen sulfi de (H
2
S)
g
nitrogen (N
2
).
strong covalent bond
d
hydrogen chloride (HCl)
2
Explain why the water molecule in Figure 3.27 is V-shaped.
I
Figure 3.30
Strong covalent and weak intermolecular forces in iodine.
