Achievement Standard

Excellence Exemplar (2025)

Curriculum

Types of Materials

Metallic Substances

What are Metallic Substances?

Metallic substances in chemistry are either pure metal elements or alloys (mixtures of metals) held together by metallic bonding. In this structure, positively charged metal ions are immersed in a mobile "sea" of delocalized valence electrons.

Structure of Metals

The structure of metals is described as “positively charged metal ions (cations) surrounded by a sea of delocalized electrons”.

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In the solid state, metal ions form an ordered structure called a ‘lattice’. The ions are arranged in regular layers. The layers are made up of positively charged metal ions. Between the ions are ‘free to move’ valance electrons.

The outer (valance) electrons are so weakly bound to metal atoms that they are free to roam throughout the entire metal. Having “lost’ their outer electrons, individual metal atoms are like positive ions in a sea of shared electrons.

Physical:

High melting/boiling points: The strong electrostatic attraction between the metal cations and delocalised electrons requires a large amount of thermal energy to disrupt.
Electrical and Thermal Conductivity: Excellent conductors in both solid and liquid states because the delocalised valence electrons are completely free to move and carry charge or heat through the structure.
Mechanical: Malleable (can be beaten into sheets) and ductile (can be drawn into wires). When force is applied, the layers of metal ions can slide past each other without breaking the bond, because the flexible sea of electrons constantly adapts and keeps them held together.

Chemical:

Readily lose valence electrons to form positive ions (cations). They easily react with oxygen (oxidation/corrosion) and acids to produce hydrogen gas.