Electron mobility connects microscopic bonding to properties. A solid ionic lattice holds ions in place, while melted or dissolved ions can carry current. Metallic electrons can move through a solid.

The model has a domain of validity. Explain its assumptions before using it in a changed context, then compare your prediction with evidence.

• Ionic bonding attracts oppositely charged ions; covalent bonding shares pairs; metals have delocalized electrons.
• Solid ionic compounds usually cannot conduct, even though they contain charges. Covalent network solids differ from small molecular substances.