Positive ions attract negative ions in all directions and become surrounded by them.

The opposite is true of negative ions - so a three dimensional structure is made of alternating anion and cations.

We call this an Ionic Lattice.

The picture right shows what a simple lattice might look like if we could see one but it's difficult to draw and difficult to see what is happening inside this lattice.

You can't even see that there is one Chloride ion for every one Sodium ion, let alone how many near neighbours each ion has.

So, although it reflects reality quite well, this isn't the best way to draw an NaCl lattice

A slightly simpler diagram is shown beneath.

Here it is obvious that the central Na⁺ ion is strongly attracted to 6 Cl^- ions, and the same would be true of any ion in the centre of a NaCl lattice.

This is not the only arrangement of ions possible in a lattice.

But it is the only lattice that you can be asked to draw in an examination and the examiner hasn't asked for it yet.

If (s)he does, you can get away with only drawing one small cube containing 4 ions instead of the eight small cubes shown here (see below)

• 1. Start with a single vertical square.

  2. Add another.

  3. Join them.

  4. Add ions of one colour in opposite corners.

  5. Add ions of another colour in the remaining corners.

  6. Make a key.