How many potassium atoms are in 250.0 grams of potassium?
1.66 x 10−24 atoms k
3.85 x 1024 atoms k
1.51 x 1026 atoms k
5.88 x 1027 atoms k

Use the atomic mass of potassium, k, 39.1 g/mol, and the formula n = mass / atomic-mass.

Where n is the number of moles.

n = 250.0 g / 39.1 g/mol = 6.3939 mol.

Now multiply by Avogadro number to find the number of atoms:

6.3939 mol * 6.02*1023 atoms/mol = 38.49 * 10^23 atoms = 3.849 * 10^24.

3.85*10^24