KEY2CHEM

Bonding in Metals and their Alloys

The electron sea model of metallic bonding states that valence electrons are delocalized and “float” loosely connected to metal cores (metal nuclei and their core electrons). These delocalized electrons give metals their characteristic properties such as ability to conduct electrical current and heat via the delocalized electrons. The properties of malleability (ability to be hammered into sheets) and ductility (ability to be pulled into wires) are also consequences of the delocalized electrons being able to move past one another during application of stress. Alloys of metals often retain this sea of delocalized electrons and so have similar properties to pure metals.

Example 1.

Which is a characteristic of metals and their alloys?

A. brittle

B. malleable

C. very high melting point

Solution

B. malleable

Because the electrons in metals and their alloys are delocalized, as described by the electron sea model, metals can be deformed into sheets or other shapes (are malleable).

Example 2.

Which substance is expected to conduct electricity in its solid state?

A. $$\require{mhchem}\ce{Cu}$$

B. $$\require{mhchem}\ce{CuCl2}$$

C. $$\require{mhchem}\ce{Cl2}$$

Solution

A. $$\require{mhchem}\ce{Cu}$$

Because the electrons in metals are delocalized, metals can conduct both electricity and heat in the solid state. Ionic compounds conduct electricity in solution or when melted but not in the solid state.

Example 3.

Which solid is expected to be a poor conductor of heat at room temperature?

A. Boron

B. Copper

C. Iron

Solution

A. Boron

Metals, such as copper and iron, are expected to be good conductors of heat because their delocalized electrons can transfer kinetic energy throughout the solid.