To the nearest whole number, how many moles are in a 120-gram sample of calcium metal? How many atoms is this?

We are given with

120 g Calcium

The molar mass of Calcium is 40 g Ca / mol Ca. Using this to determine the number of moles

120 g (1 mol / 40 g) = 3 mol

We use the Avogadro's number to convert moles to number of atoms

3 mol (6.022 x 10^23 atoms / 1 mol) = 1.81x10^24 atoms