Chemistry Reference
In-Depth Information
There are times when no single Lewis dot diagram for a compound can
be considered to be the only possible structure. In such a situation, a series
of diagrams are used to represent all of the possible structures, which are
said to exist simultaneously. The series of diagrams are collectively referred
to as resonance structures.
Lewis dot diagrams are also
useful for illustrating a special type
of covalent bond, called a coordi-
nate covalent bond. A coordinate
covalent bond is formed when both
electrons that become a shared
pair of electrons between two at-
oms are provided by only one of
the atoms. In other words, an atom
with a strong attraction for elec-
trons can combine with an atom
that has already satisfied its desire
for a noble gas configuration and
force it to share a pair of unshared
electrons. It is in this way that the
The Correct Lewis Dot Notation for
Carbon Tetrachloride
Cl
Cl
C Cl
Cl
Each atom in the compound is
surrounded by 8 electrons,
completing its octet.
Figure 4-3e
neutral compound called ammonia (NH
3
) can combine with a hydrogen
ion (H
+
) to become the polyatomic ion called the ammonium (NH
4
+
) ion,
as shown in Figure 4-3f.
Hydrogen Ion Reacting With Ammonia to Form the Ammonium Ion
H
H
+
H
+
+
N H
H
N H
H
H
When the ammonia molecule provides both electrons that get shared with
the H
+
ion, a coordinate covalent bond is formed.
Figure 4-3f
