How many moles of sulfur are found in 2.86 * 10^21 atoms of sulfur?

Explanation:

Hello!

In this case, since the Avogadro's number is a large one that help us to figure out 1 mole of any substance contains 6.022x10²³ particles, say atoms, molecules or ions, in this case, for the given amount of atoms of sulfur, the corresponding moles are obtain down below:

Best regards!

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)