Drawing ionic lewis structures

[Andrew Nguyen 2I]

For ionic compounds, I saw a lot of lewis structures drawn with one ion in a bracket and the other ion outside of the bracket. For example in the solutions manual, for K3P it shows phosphorus in a bracket with the three potassiums on the outside. How do we know which ion belongs outside or inside a bracket,or does it not matter.

[Chem_Mod]

As I did in class the anion usually has the lone pairs and therefore usually has the bracket to indicate all the electrons within the bracket belong to that anion.