What is the formula for mercury(I) nitrite?

The correct formula for mercury(I) nitrite is represented by Hg2(NO2)2. This compound contains mercury in the +1 oxidation state, which is often indicated as mercury(I).

Mercury(I) exists as a dimer, which means that it forms pairs of mercury atoms. In this case, two mercury atoms are linked together, indicated by the use of the Hg2 notation. Each mercury(I) ion is +1 charged, resulting in a total charge of +2 from the two mercury atoms when they form the dimer.

The nitrite ion (NO2) has a -1 charge. Therefore, to balance the +2 charge from the dimerized mercury, two nitrite ions are required, thus giving the full formula of Hg2(NO2)2. This shows that both nitrite ions contribute -1 charge each, perfectly countering the +2 charge from the paired mercury ions.

In this context, other options do not fit for various reasons. For instance, Hg(NO2) denotes a single mercury ion paired with one nitrite ion, which would imply that the mercury is in a +2 state and does not adhere to the +1 state of mercury(I). Similarly, Hg(NO2)2 suggests