Answer
(a) $4.664\times10^{-23}\,g$
(b) $9.273\times10^{-23}\,g$
Work Step by Step
(a) Molar mass of Si=$28.0855\,g/mol$
That is, the mass of $6.022\times10^{23}$ Si atoms is equal to 28.0855 g.
$\implies$ mass of 1 Si atom=$\frac{28.0855\,g}{6.022\times10^{23}}=4.664\times10^{-23}\,g$
(b) Molar mass of Fe=$55.845\,g/mol$
That is, the mass of $6.022\times10^{23}$ Si atoms is equal to 55.845 g.
$\implies$ mass of 1 Fe atom=$\frac{55.845\,g}{6.022\times10^{23}}=9.273\times10^{-23}\,g$
