The atomic mass of Al is 26.98154 g/mol. Is it possible to have 5.0 x 10^-25 g of Al?

First let us calculate the number of moles.

number of moles = (5.0 x 10^-25 g) / (26.98154 g/mol)

number of moles = 1.853 x 10^-26 mol

We then calculate the number of atoms using Avogadros number.

number of atoms = (1.853 x 10^-26 mol) * (6.022 x 10^23 atoms / mole)

number of atoms = 0.011 atoms

There can never be an atom of less than 1 since 1 unit of atoms is the basic unit of all elements. Therefore it is NOT possible.