KEY2CHEM

Structure and Properties of Metallic Solids

As described by the electron sea model, bonding in metals is composed of metal cores (composed of metal nuclei and inner electrons) surrounded by delocalized valence electrons. These valence electrons are not tightly affixed to any single metal core, and the movement of these valence electrons gives metallic solids their unique properties. For example, metals are good conductors of electricity and of heat because the delocalized electrons can carry the charge and heat.

Example 1.

Which is a property of metallic solids?

A. brittle

B. conductive

C. low melting point

Solution

B. conductive

Metallic solids are good electrical and thermal conductors due to the delocalized electrons. Metallic solids can be deformed into shapes (are malleable) because the metallic cores slide past one another to avoid repulsions. Metallic solids generally have relatively high melting points, due to the energy required to disrupt the cumulative electrostatic forces holding metal cores to delocalized electrons.

Example 2.

Which is NOT a property of metallic solids?

A. malleable

B. lustrous

C. brittle

Solution

C. brittle

Metallic solids are malleable (can be deformed into shapes) because the metal cores and delocalized electrons slide past like-charged particles to avoid repulsions. Metallic solids also reflect light, which gives them a lustrous (shiny) appearance.

Example 3.

Which substance is expected to have the highest boiling point?

A. $$\require{mhchem}\ce{Cu}$$

B. $$\require{mhchem}\ce{CO2}$$

C. $$\require{mhchem}\ce{CH4}$$

Solution

A. $$\require{mhchem}\ce{Cu}$$

Metallic solids have high boiling points because the delocalized electrons are attracted to many neighboring metal nuclei. These cumulative interactions require more energy to break apart, resulting in higher boiling points.