8.3 Metallic Bonds
8.3 Metallic Bonds
Lesson Objectives
- Describe the electron-sea model of metallic bonding.
- Explain how metallic bonding is responsible for the conductivity and luster of metals.
- Explain why metals are malleable and ductile, while crystalline ionic compounds are not.
- Describe how metal atoms are arranged, including the three most common packing systems.
- Identify some common alloys and explain their importance.
Lesson Vocabulary
- alloy
- closest packing
- metallic bond
Check Your Understanding
Recalling Prior Knowledge
- How are the cations and anions in an ionic crystal arranged?
- What happens to an ionic crystal when it is put under a large stress?
The bonding that occurs in a metal is responsible for its distinctive properties, including luster, malleability, ductility,
and excellent conductivity.
The Metallic Bond
Pure metals are crystalline solids, but unlike ionic compounds, every point in the crystal lattice is occupied by an
identical atom. The electrons in the outer energy levels of a metal are mobile and capable of drifting from one metal
atom to another. This means that the metal is more properly viewed as an array of positive ions surrounded by a
“sea of mobile valence electrons.” Electrons which are capable of moving freely throughout the empty orbitals of the
metallic crystal are called delocalized electrons (Figure8.11). Ametallic bondis the attraction of the stationary
metal cations to the surrounding mobile electrons.