Note the formula
[tex]\boxed{\sf No\:of\:atoms=No\:of\:moles\times Avagadro\:no}[/tex]
Find no of moles
[tex]\\ \tt{:}\dashrightarrow \dfrac{8.78g}{32g/mol}[/tex]
[tex]\\ \tt{:}\dashrightarrow 0.27mol[tex]
No of atoms
[tex]\\ \tt{:}\dashrightarrow 0.27\times 6.023\times 10^{23}[/tex]
[tex]\\ \tt{:}\dashrightarrow 1.6\times 10^{23}atoms[/tex]
