Here's why:

* Aluminum (Al) is a metal, and metals tend to lose electrons to form positive ions (cations).

* Nitrate (NO₃⁻) is a polyatomic ion with a negative charge.

In aluminum nitrate (Al(NO₃)₃), the aluminum atom loses three electrons to form an Al³⁺ cation. Each nitrate ion carries a -1 charge. The three nitrate ions balance out the +3 charge of the aluminum ion, resulting in a neutral compound.

Ionic bonds are formed through electrostatic attraction between oppositely charged ions.