Answer
$5.6\times10^{20}\ atoms\ Sr $
Work Step by Step
1.Use the molar mass of strontium and Avogadro's number as conversion factors in order to determine the number of atoms of strontium.
2. $0.082 g\ Sr \times\frac{1\ mol\ Sr}{87.62\ g\ Sr}\times\frac{6.022\times10^{23}}{1\ mol\ Sr}= 5.6\times10^{20}\ atoms\ Sr $
