Here's how to figure out the number of atoms in a sulfate ion:

* The Formula: The sulfate ion is written as SO₄²⁻.

* Breaking it Down:

* S: This represents one sulfur atom.

* O₄: This represents four oxygen atoms.

* Total: Therefore, a sulfate ion (SO₄²⁻) contains a total of 5 atoms (1 sulfur + 4 oxygen).