We can find the number of moles of a compound based on their number of atoms using Avogadro's number which says that there are 6.022 x 10^(23) atoms in 1 mol.
[tex]4.2\cdot10^{28}atoms\text{ Zn}\cdot\frac{1\text{ mol Zn}}{6.022\cdot10^{23}atoms\text{ Zn}}=69744.27\text{ moles Zn.}[/tex]The answer is that there are 69744.27 moles of zinc in 4.2 x 10^(28) atoms of zinc.
