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Ionic Bonding and Properties

This page explains how non-metal and metal ions interact with each other and form ionic bonds. It then looks at how the ionic bond gives ionic compounds their properties, such as high melting and boiling points. If you find this page confusing you may need to review your knowledge of ions, this information can be found here.

By the end of this page you should be able to:

  • Recognise an ionic lattice
  • Describe an ionic bond
  • Explain the properties of ionic compounds

Crystal Lattice / Ionic Lattice / Giant Lattice

Ionic compounds are giant structures, this means that they consist of large numbers of ions. An ionic compound is made of metallic and non-metallic ions, metal ions have a positive charge and non-metal ions have a negative charge. The oppositely charged ions attract each other (can also be called an electrostatic attraction) and form a crystalline lattice like the one shown to the right. These attractions go in all dirsctions.

In a crystalline lattice the particles are arranged to maximise the attractive forces between the ions, or in simpler terms the non-metal and metal ions alternate. This is shown in the diagram to the right, you're expected to know the 2D structure of sodium chloride.If you're asked to draw this in an exam - you must draw the 2D form containing at least 9 ions in a 3 x 3 grid.

2D Diagram of a Sodium Chloride Crystal Lattice

2D representation of a crystal lattice.

3D Ball and stick model of a crystal lattice

3D representation of a crystal lattice.


Physical Properties of Ionic Compounds

Ionic Compounds have the following physical properties:

  • Hard
  • High melting and boiling points
  • Conduct when molten or dissolved

Explaining The Physical Properties of Ionic Compounds

Explaining the properties of ionic compounds features in every higher tier exam and are worth a minimum of 2 marks, normally 4 for hardness and melting/boiling point, so learn these model answers off by heart. Simplified questions worth two marks normally appear in the foundation tier.

Hardness

Ionic substances are hard because there are strong electrostatic attractions between oppositely charged ions in a giant structure, therefore a lot of force is needed to overcome this attraction and break the ions apart.

High Melting and Boiling Points

Ionic substances have high melting and boiling points because there are strong electrostatic attractions between oppositely charged ions in a giant structure, therefore a lot of energy is needed to overcome this attraction and break the ions apart.

Conductivity

When molten or dissolved the ions are able to move, so charge can flow freely.

N.B. The charge in this case is the physical movement of the ions. Be careful when looking at older markschemes - AQA have changed what they will allow as an acceptable answer to this question.

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