Here's why:

* Ionic compounds are formed by the electrostatic attraction between positively charged ions (cations) and negatively charged ions (anions).

* Sodium monofluorophosphate consists of:

* Sodium ions (Na+) which are positively charged.

* Monofluorophosphate ions (PO3F2-) which are negatively charged.

The strong electrostatic attraction between these oppositely charged ions holds the compound together.