What condition must be met when writing a formula for an ionic compound

The charge of ions must be balance

Explanation:

Ionic compound: It is that compound which consist of positive and negative ions and ions held together by electrostatic force. Electric force is that force which act between two charges.

The compound is neutral because negative ions is equal to positive ions in the ionic compound.

The charge of ions must be balance. It is necessary condition for writing a formula for an ionic compound.

Hence, the charge of ions must be balance is that condition which must be met when writing a formula for an ionic compound.