This can be done with some simple dimensional analysis. First you convert your gram of gold into moles of gold There are 196.97 grams of gold for every one mole of gold so you divide 4.27 by 196.67 to get 0.0217 moles of gold. You then multiply the moles of gold by Avogadro's number, 6.02 X 10^23. Avogadro's number indicates the number of atoms in one mole. Therefore, there are 1.307 X 10^22 atoms in 4.27 grams of gold.