1 atom of iron weighs

 $1\text{\hspace{0.17em}mole}=6\times {10}^{23}\text{\hspace{0.17em}iron\hspace{0.17em}atoms}\to 56\text{\hspace{0.17em}g\hspace{0.17em}of\hspace{0.17em}iron}$

$\text{1Iron\hspace{0.17em}atom\hspace{0.17em}}\to x\text{g\hspace{0.17em}of\hspace{0.17em}iron}$

$56\times 1=x\times 6\times {10}^{23}$

$x=\frac{56}{6\times {10}^{23}}=9.33\times {10}^{-23}\text{g}$