Explicit science instruction
Metallic solids are modeled as positive ion cores surrounded by mobile, delocalized valence electrons. The attraction between the cores and shared electron cloud holds the solid together.
Because electrons are mobile through the structure, many metals conduct electricity in the solid state. Because bonding is not limited to one rigid directional pair, layers of atoms can shift without immediately destroying all bonding.
The model is qualitative: conductivity and strength also depend on composition, defects, temperature, and crystal structure.
Vocabulary: metallic bonding; delocalized electron; conductivity; malleability; lattice.
Worked example with reasoning
Copper conducts as a solid because mobile electrons can respond to an electric field. An ionic crystal can contain charged particles yet fail to conduct in the solid state because its ions are not free to move.
Guided question
Why does the metallic model explain both conductivity and malleability better than a model of isolated atom pairs?
Independent work
- Compare metallic and ionic particle models.
- Explain solid-state conductivity in each.
- Draw how a metal layer can shift while delocalized bonding persists.
Misconception check
Metals do not conduct because whole atoms flow through the wire; charge transport is associated with mobile electrons.
Formative understanding check
Why can a solid metal conduct while a solid ionic crystal often cannot?
Reveal response
The metallic model contains mobile electrons, while ions in an ionic solid are fixed in lattice positions.
Mentor evidence conference
Ask Archaemenes to challenge the structure–property reasoning and identify unsupported assumptions.
Teacher guidance
Foundation: Match properties to particle-level features.
Core: Explain conductivity and malleability with the delocalized-electron model.
Extended: Discuss how alloying or defects can change simple metallic-property predictions.