Answer
$ 0.187\ g\ He $
Work Step by Step
1. Use Avogadro's number and the molar mass of helium as conversion factors in order to determine the number of grams of helium.
2. $2.82\times10^{22}\ atoms\ He\times\frac{1\ mol\ He}{6.022\times 10^{23}\ atoms\ He}\times\frac{4\ g \ He}{1\ mol\ He} = 0.187\ g\ He $
