CIE AS Chemistry (9701) exams from 2022

Revision Notes

1.4.3 Lattice Structures

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

States of Matter Ionic Lattice, downloadable AS & A Level Chemistry revision notes

Ionic lattices of the ionic compounds NaCl and MgO

 

States of Matter General Ionic Lattice, downloadable AS & A Level Chemistry revision notes

General ionic lattice which shown the actual packing of the ions

Covalent lattices

  • Covalent bonds are bonds between nonmetals 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

States of Matter Simple Molecular Lattice, downloadable AS & A Level Chemistry revision notes

Simple molecular lattices

 

States of Matter Giant Molecular Lattice, downloadable AS & A Level Chemistry revision notes

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

 

States of Matter Metallic Lattice, downloadable AS & A Level Chemistry revision notes

Layers of copper ions (the delocalised electrons are not shown in the diagram)

Exam Tip

Graphite, diamond and buckminsterfullerene are allotropes of carbon.

They are different structural forms of the same element (which is carbon).

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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