Question

number of atoms in 0.500 mole of Al

Answer 1

multiply that number by the Avogadro's number!!!

Answer 2

One mole of anything contains Avagodro's number of atoms, molecules, etc. That is 6.02x10^23.
So, 1 mole Al contains 6.02x10^23 atoms of Al. 0.5 moles of Al will contain one-half that many atoms or 3.01x10^23 atoms of Al