Answer
1 Iron (Fe) atom
2 Nitrogen (N) atoms
4 Oxygen (O) atoms
Work Step by Step
In the formula $Fe(NO_{2})_{2}$, there is only 1 Iron atom because there is no subscript beside "Fe" indicating that there is only one of that atom. However, the nitrogen atom does not have only one atom because it is in brackets with a subscript of 2, indicating that nitrogen has 2 atoms. It's the same for oxygen: although oxygen already has 2 as its subscript, it is also in brackets with 2 as the subscript. So Oxygen has 4 atoms in this formula, as these are multiplicative.
