Answer : The correct option is, [tex]Fe_2O_3[/tex]
Explanation :
Formula unit of a compound is defined as the minimum number ratio of ions represented in the compound.
The valency of iron is (+3) and the valency of oxygen is (-2). By the criss-cross method the [tex]Fe^{+3}[/tex] cation combine with the [tex]O^{2-}[/tex] anion, it will give [tex]Fe_2O_3[/tex].
[tex]Fe^{+3}+O^{2-}\rightarrow Fe_2O_3[/tex]
The formula by criss-cross method is shown below.
