A dot and cross diagram shows:
However, it does not show how the ions are arranged in space.
A dot and cross diagram for sodium chloride suggests that it is made up of pairs of sodium and chloride ions. It is not.
Sodium chloride has a giant ionic lattice structure with equal numbers of sodium and chloride ions.
The ionic lattice structure of an ionic compound needs a 3D model, or a 2D representation of a 3D model.
A 3D construction model shows how the ions are arranged in a lattice structure. These models usually use coloured balls to represent the ions. Some use sticks to show the ionic bonds.
A 3D construction model still has limitations:
A 3D model may be drawn as a 3D diagram. The limitations are the same as the 3D construction model.
On a computer it may be possible to rotate this diagram to look at it from different angles. This helps to visualise the structure.
A 2D representation is the easiest model to draw.
A 2D model shows the arrangement of one layer of ions but it does have a major additional limitation - it does not show where the ions are located on the other layers. This is important because there are different possible arrangements of ions.
Use the 3D model and diagrams to help you draw the next row of sodium chloride in a 2D model.
In sodium chloride the ions are arranged alternately so, in the next row, chloride ions are located above the sodium ions.