* Ammonium ion (NH₄⁺): This is a polyatomic cation formed by the covalent bonding of one nitrogen atom and four hydrogen atoms. The overall charge of the ion is +1.

* Fluoride ion (F⁻): This is a monatomic anion formed by the gain of one electron by a fluorine atom. The overall charge of the ion is -1.

Ionic bonds form between oppositely charged ions. In ammonium fluoride, the positively charged ammonium ion (NH₄⁺) forms an electrostatic attraction with the negatively charged fluoride ion (F⁻). This attraction holds the ions together in a crystal lattice structure, forming the ionic compound ammonium fluoride.