Answer
$8.06\times10^{28}\ atoms\ He $
Work Step by Step
1. Use the molar mass of helium and Avogadro's number as conversion factors in order to determine the number of helium atoms.
2. $536\times10^{3} g\ He \times\frac{1\ mol\ He}{4\ g\ He}\times\frac{6.022\times10^{23}}{1\ mol\ He}= 8.06\times10^{28}\ atoms\ He $
