Question: how many atoms are in 1 gram of aluminum?
Answer: This means that the mass of one mole of aluminium atoms will be 26.982 g . As you know, one mole of any element contains exactly 6.022⋅1023 atoms of that element. This means that if you know how many moles of aluminium you have in 4.55 g , you can use Avogadro's number to find the number of atoms.