The Lattice Structure

  • In lattice structures the atoms form a regular shaped structure.
  • The lattices formed by ionic compounds consist of a regular arrangement of alternating positive and negative ions in which the ions are closely packed together.
  • Strong electrostatic forces of attraction are present between the oppositely charged ions.
  • These strong forces act in all directions and form the basis of ionic bonding.
  • This causes ionic compounds to have high melting and boiling points.

Ionic lattice structures, IGCSE & GCSE Chemistry revision notes

Representing the lattice structure of NaCl

  • The lattice arrangement is present in three dimensions which allows solid ionic compounds to form regular shapes.
  • Solid ionic crystals contain huge numbers of ions hence they form giant ionic lattices.

Ball and Stick Ammonia, IGCSE & GCSE Chemistry revision notes

Image showing magnified crystals of NaCl where the regular shapes can be seen

Naming Ionic Compounds

  • The ending -ide means the compound contains two elements where one is a metal and the other a non-metal.
  • The name of the metal atom comes first and the ending of the second atom is replaced by adding -ide.
    • E.g. NaCl which contains sodium and chlorine thus becomes sodium chloride.
  • If both atoms are non-metals and one of those is hydrogen, then hydrogen comes first.
    • E.g. hydrogen and chlorine combined is called hydrogen chloride.
  • For other combinations of nonmetals as a general rule, the element that has a lower Group number comes first in the name.
    • E.g. carbon and oxygen combine to form CO2 which is carbon dioxide since carbon is in Group 4 and oxygen in Group 6.
  • The ending -ate means the compound contains a minimum of three elements where one of them is oxygen.
  • Some common ions which form part of these compounds include the carbonate ion (CO32-), sulfate ion (SO42-) and the nitrate ion (NO3).
  • When these ions form a compound with a metal atom, the name of the metal comes first.
  • E.g. KNO3 is potassium nitrate, CaCO3is calcium carbonate.
  • A list of the common ions and their formulae is shown below.

Common Ions Table, IGCSE & GCSE Chemistry revision notes

  • For ionic compounds you have to balance the charge of each part by multiplying each ion until the sum of the charges = 0.
  • Example: what is the formula of aluminium sulfate?
    • Write out the formulae of each ion, including their charges.
    • Al3+  SO42-
  • Balance the charges by multiplying them out: Al3+ x 2 = +6 and SO42- x 3 = -6; so +6 – 6 = 0.
  • So the formula is Al2(SO4)3

AQA GCSE Chemistry Notes

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.