2.2.2 (b) Ionic Lattice Structure

Again, you don't need to know much more about Ionic Lattices than you did at GCSE.

Ions typically pack into extremely regular crystalline structures, in an arrangement that maximises attractions and minimises repulsions).

For ions of a similar size where the charges match (eg NaCl where we have Na⁺ and Cl^-) the arrangement is the one we have seen before.

The Anions attract all the nearby Cations (and vice versa).

An expanded diagram (left) is more informative.

Because the ions fit together in this manner we can see the Sodium ion (Na⁺) in the centre (blue) is particularly close to 6 Chloride ions (Cl^-) above, below, in front, behind and to the left and right of it.

These are strong attractions due to the closeness.

It is also repelled by the other 12 Sodium ions diagonally across from it in each cube.

But these repulsions are cancelled out by equal attractions to 12 diagonal Chloride ions.

So we can ignore diagonal forces and the lines on the diagram above show the overall attractions only.

Again, the space-filling model isn't actually very helpful to look at.

Even if it is a more accurate representation of Caesium Chloride's lattice.