Which has more number of atoms:

100 grams of Magnesium or 100 grams of Aluminium

(Given: At mass of Mg=24 u, AL = 27 u)

100 grams of magnesium:

1 mole of Mg atom = 6.022 × 10²³ atoms

This means 24g of Mg has 6.022 × 10²³ atoms

Then 100 g contains:

Number of Mg atoms = 2.5 × 10²⁴ atoms

100 grams of aluminium:

1 mole of Al atom = 6.022 × 10²³ atoms

This means 27g of Al has 6.022 × 10²³ atoms

Then 100 g contains:

Number of Al atoms = 2.2 × 10²⁴ atoms

Thus, 100g of magnesium has more atoms.