Mercury(I) nitride is a bit tricky because mercury(I) ions are actually diatomic, meaning they exist as Hg₂²⁺.

Here's how to determine the formula:

* Mercury(I) ion: Hg₂²⁺

* Nitride ion: N^3-

To balance the charges, we need three Hg₂²⁺ ions (6+ charge) and two N^3- ions (6- charge).

Therefore, the formula for Mercury(I) nitride is Hg₆N₂.