Chemistry Reference
In-Depth Information
Carbon
Silicon
Oxygen
(a) Diamond
(b) Graphite
(c) Silicon dioxide
Figure 14.2
Tiny Portions of Structures of Three Macromolecular Solids
The structures extend almost indefinitely in all directions, left and right, up and down, in and out.
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
Twenty years ago Robert Curl, Harold Kroto, and Richard Smally discov-
ered that carbon exists in a new form, with 60 atoms covalently bonded
in the shape of a ball (Figure 14.3).
ITEM OF INTEREST
EXAMPLE 14.2
(a) Is the 60-carbon molecule a macromolecular form of carbon?
(b) Would you expect its melting point to be as high as that of
graphite?
Solution
(a) No, although a large molecule, it is not macromolecular.
(b) Its melting point is much lower.
EXAMPLE 14.3
The 60-Carbon
Figure 14.3
How many pairs of ions are included in a tiny cube of rock salt, if 250,000
sodium ions occur on each edge in the three perpendicular directions?
Molecule
The 60-carbon molecule in the shape
of a geodesic dome is named after the
architect who designed the dome,
Buckminster Fuller. The molecule's
nickname “Buckyball” is catchier
than its full name—Buckminster
fullerene.
Solution
10
5
)
3
10
16
The cube contains sodium ions. There are also
chloride ions in this tiny particle of NaCl. (Remember that 1.00 mol,
or 58.5 g, of NaCl includes
(2.5
1.6
10
16
1.6
10
23
6.02
formula units of NaCl, about 39 million
times as many as in this tiny cube.)
