Chemistry Reference
In-Depth Information
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Positive ion
Negative ion
Figure 14.1
Sodium Chloride
Structure
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The regularity of the units is characteristic of crystalline solids. The sodium
chloride structure (also called the rock salt structure) is an example of an ionic
lattice (Figure 14.1). Diamond, graphite (pencil “lead”), and silica (sand) are exam-
ples of network lattices (Figure 14.2). Molecular solids include such solids as ice
and naphthalene (mothballs), Most elemental metals are examples of
metallic solids. Regardless of their specific classifications, all crystalline solids are
characterized by regularly repeating arrangements of their component particles.
C
10
H
8
.
EXAMPLE 14.1
(a)
What is the difference between a stack of concrete blocks and a concrete
wall?
(b)
The atoms in both network (macromolecular) and molecular solids are
covalently bonded. What is the difference in their structures?
Solution
(a)
The concrete in each block in a stack is held firmly to the rest of that
block, but the blocks are not held tightly to one another. The concrete
wall is held together tightly from one end to the other.
(b)
In molecular solids, a few to hundreds of atoms (or even thousands of
atoms in polymeric substances such as plastics) are bonded into each
molecule, as for example in or These individual
molecules are held to one another by intermolecular forces. In macro-
molecular solids, covalent bonds connect all the atoms—hundreds of
thousands or even millions of them—in a network (see Figure 14.2).
I
2
,
P
4
O
10
,
C
6
H
12
O
6
.
Practice Problem 14.1
What type of solid is described by each of
the following statements?
(a)
Fourteen atoms are bonded in each molecule.
(b)
About 500 million ions are bonded to one another.
(c)
About 500,000 atoms are bonded to one another with covalent bonds.
