No, ammonium ion (NH₄⁺) does not form an insoluble salt with carbonate (CO₃²⁻).

Here's why:

* Solubility Rules: Ammonium salts are generally soluble in water. This means that ammonium carbonate ((NH₄)₂CO₃) would be soluble.

* Ionic Compounds: Ammonium carbonate is an ionic compound formed from the ammonium cation (NH₄⁺) and the carbonate anion (CO₃²⁻).

Therefore, ammonium carbonate is a soluble salt, not an insoluble one.