To determine the mass of the number of atoms, the first step is to convert this number of atoms to moles using Avogadro's number:
[tex]3.06\times10^{21}atoms\cdot\frac{1molAs}{6.022\times10^{22}atoms}=0.051molAs[/tex]Convert this amount of moles to grams using the molecular weight of Arsenic:
[tex]0.051molAs\cdot\frac{74.9g}{1molAs}=3.8199g[/tex]It means that the answer is 3.8199g.
