(10 points)
use the periodic table to determine how many atoms of phosphorus (p) are in a sample that has a mass of 172.90 g.

a. 3.48 × 1021 atoms

b. 1.97 × 1022 atoms

c. 3.36 × 1024 atoms

d. 1.04 × 1026 atoms

Avogadro's number represents the number of units in one mole of any substance. This has the value of 6.022 x 10^23 units / mole. This number can be used to convert the number of atoms or molecules into number of moles. We do as follows:

 172.90 g ( 1 mol / 30.97 g ) (6.022 x 10^23 atoms / mol) = 3.36 × 10^24 atoms

Therefore, option C is the answer.