Here's why:

* Hg₂²⁺ is the mercury(I) ion. It's important to note that mercury can have two common oxidation states: +1 (Hg₂²⁺) and +2 (Hg²⁺). The subscript "2" in the formula indicates that two mercury atoms are bonded together to form this ion.

* I⁻ is the iodide ion.

Therefore, the correct name combines the cation (mercury(I)) and the anion (iodide) to form Mercury(I) iodide.