The ionic bond

Substances with ionic bonds are neutral, just because they contain as much negative ions (charges) as they have positive ions (charges).
Positive and negative ions always stick toghether in such a way that the result is a neutral substance: with equal positive and negative charges.

The positive and negative ions very neatly are packed toghether in a fixed proportion and in incredible large amounts in an: IONIC LATTICE

The proportion in which the ions stay toghether is indicated with numbers right under, as if it were a molecular formula, but in fact this is a PROPORTIONAL FORMULA.
Att.: At a first look there seems to be no difference between proportional and molecular formulas.