Answer
$3.24\times 10^{-22}\ g\ Pt $
Work Step by Step
1. Use Avogadro's number and the molar mass of platinum as conversion factors in order to determine the mass of the platinum atom.
2. $1\ atoms\ Pt\times\frac{1\ mol\ Pt}{6.022\times 10^{23}\ atoms\ Pt}\times\frac{195\ g \ Pt}{1\ mol\ Pt}= 3.24\times 10^{-22}\ g\ Pt $
