A modern penny weighs 2.5 g but contains only 0.063 g of copper (cu). how many copper atoms are present in a modern penny?

The molar mass of copper is 63.546 g/mol. Therefore calculating for moles:

moles = 0.063 g / (63.546 g / mol) = 9.91 x 10^-4 mol

Using Avogadros number, we get the number of Copper atoms.

atoms = 9.91 x 10^-4 mol * 6.022 x 10^23 atoms/mol

atoms = 5.97 x 10^20 atoms