The chemical formula for iron(II) nitrate isFe2(NO3)3.Ir(NO2)2.Fe2N3.Fe(NO3)2.Fe(NO2)2.

The correct chemical formula for iron(II) nitrate is $\text{Fe(NO}_3\text{)}_2$.

Here's a breakdown of the other compounds mentioned:

1. Iron(III) nitrate is represented as $\text{Fe(NO}_3\text{)}_3$.
2. Iron(II) nitrite is represented as $\text{Fe(NO}_2\text{)}_2$.
3. Iron(III) nitride is $\text{Fe}_2\text{N}_3$.

Among the options given:

• $\text{Fe(NO}_3\text{)}_2$ is the correct formula for iron(II) nitrate.
• The other compounds listed do not represent iron(II) nitrate.

Iron(II) nitrate is commonly used in various applications such as a reagent in chemical reactions and as a fertilizer, and it's important to distinguish it from its other oxidation states.