# How many moles of potassium are there in 2.4 \times 10^21 atoms K?

Nov 21, 2017

$2.4 \cdot {10}^{21} \text{atoms of K"*("1 mol of K"/(6.022*10^23 "atoms")) = 0.0040 "mols of K}$
Since there are $6.022 \cdot {10}^{23}$ atoms in 1 mol of a substance (Avogadro's number), we use that conversion factor in the dimensional analysis.