Lattice Structures (Cambridge (CIE) A Level Chemistry): Revision Note

Lattice Structures

• Most ionic, metallic and covalent compounds are crystalline lattice

• The ions, atoms or molecules are arranged in a regular and repeating arrangement

Giant ionic lattices

• An ionic bond is an electrostatic force between a positively charged metal (cation) ion and a negatively charged non-metal (anion) ion

  • The metal becomes positively charged as it transfers electrons to the non-metal becomes negatively charged

• Ionic compounds are arranged in giant ionic lattices (also called giant ionic structures)

• The type of lattice formed depends on the sizes of the positive and negative ions which are arranged in an alternating fashion

  • The ionic lattice of MgO and NaCl are cubic

Ionic lattices of the ionic compounds NaCl and MgO

General ionic lattice

Covalent lattices

• Covalent bonds are bonds between non-metals in which electrons are shared between the atoms

• Covalent compounds can be arranged in simple molecular or giant molecular lattices

  • Simple molecular lattices: Iodine, buckminsterfullerene (C₆₀) and ice

  • Giant molecular: silicon(IV) oxide, graphite and diamond

Simple molecular lattices

Giant molecular lattices 

Metallic lattices

• Metals form giant metallic lattices in which the metal ions are surrounded by a ‘sea’ of delocalised electrons

• The metal ions are often packed in hexagonal layers or in a cubic arrangement

The layered structure of copper atoms