4.Metals are malleable or ductile (or both). A crystal of a metal is easily deformed when
a mechanical stress is applied to it. All of the metal ions are identical, and they are
imbedded in a “sea of electrons.” As bonds are broken, new ones are readily formed
with adjacent metal ions. The features of the arrangement remain unchanged, and
the environment of each metal ion is the same as before the deformation occurred
(Figure 13-36). The breakage of bonds involves the promotion of electrons to
higher-energy levels. The formation of bonds is accompanied by the return of the
electrons to the original energy levels.A crystal can be cleaved into smaller
crystals that have the same
appearance as the larger crystal.
Here a worker is cleaving a large
crystal of sodium chloride.Key Terms 531A malleablesubstance can be rolled
or pounded into sheets. A ductile
substance can be drawn into wires.+ + + + + + + +
+ + + + + + + +
+ + + + + + + +
+ + + + + + + +
+ + + + + + + ++ + + + + + + +
+ + + + + + + ++ + + + + + + +
+ + + + + + + +
+ + + + + + + +ForceForce(a)
- – + – + – + – +
- – + – + – + – + –
- – + – + – + – +
- – + – + – + – + –
- – + – + – + – +
- – + – + – + – +
- – + – + – + – + –
- – + – + – + – +
- – + – + – + – +
+ – + – + – + – + –ForceForce(b)
Figure 13-36 (a) In a metal, the positively charged metal ions are immersed in a
delocalized “cloud of electrons.” When the metal is distorted (e.g., rolled into sheets or
drawn into wires), the environment around the metal atoms is essentially unchanged, and no
new repulsive forces occur. This explains why metal sheets and wires remain intact. (b) By
contrast, when an ionic crystal is subjected to a force that causes it to slip along a plane, the
increased repulsive forces between like-charged ions cause the crystal to break.
Key Terms
Adhesive force Force of attraction between a liquid and another
surface.
Allotropes Different forms of the same element in the same
physical state.
Amorphous solid A noncrystalline solid with no well-defined,
ordered structure.
Band A series of very closely spaced, nearly continuous molecu-
lar orbitals that belong to the crystal as a whole.
Band gap An energy separation between an insulator’s highest
filled electron energy band and the next higher-energy vacant
band.
Band theory of metals A theory that accounts for the bonding
and properties of metallic solids.
Boiling point The temperature at which the vapor pressure of
a liquid is equal to the external pressure; also the condensation
point.
Capillary action The drawing of a liquid up the inside of a small-
bore tube when adhesive forces exceed cohesive forces, or the
depression of the surface of the liquid when cohesive forces
exceed adhesive forces.
Cohesive forces All the forces of attraction among particles of
a liquid.