first, we need to convert the grams of gold into mole using the molar mass (molecular weight) of gold, and then into particles using avogadro's number (1 mol= 6.02 x 10^23)
molar mass of gold= 197 grams/ mole
100.0 grams (1 mole/ 197 grams) x (6.02 x 10^23 particles/ 1 mole) = 3.06 x 10^23