Question

How many atoms of mg are present in 144 g of mg

Answer 1

Mg has molar mass 24g.
So 144g mass of Mg will contain 6 moles of Mg.

Answer 2

$n_{moles}=\frac{144}{24}=6 moles\\\\number\:of\:atoms=6×N_a=3.613×10^{24}$