The density of solid Cr is 7.15 g/cm3. How many atoms are present per cubic centimeter of Cr?

To calculate the number of atoms of Cr, we first find the number of moles per unit of cubic centimeter of Cr. Then, use avogadros number for the number of atoms. Calculations are as follows:

1 cm^3 (7.15 g/cm^3) (1 mol / 51.996 g Cr) = 0.14 mol Cr

0.14 mol Cr (6.022 x 10^23 atoms Cr / 1 mol Cr) = 8.28 x 10^22 atoms Cr