Here's why:

* Copper (Cu) is a metal, and metals tend to lose electrons to form positively charged ions (cations).

* Sulfate (SO₄²⁻) is a polyatomic ion with a negative charge (anion).

* Ionic bonds form when a metal loses electrons to a nonmetal, creating a strong electrostatic attraction between the oppositely charged ions.

In copper sulfate (CuSO₄), the copper ion (Cu²⁺) loses two electrons, which are gained by the sulfate ion (SO₄²⁻) to create a stable compound.