Question

which has more number of atoms: 50 grams of potassium or 50 grams of calcium?

Answer 1

Atomic mass of Al = 27 u
So 27 gms of Aluminum contains N = 6.022*10²³ atoms
50 gms of Al contains : 50 N/27 atoms

Atomic mass of Fe = 56 u
So 56 gms of Fe contains N atoms
50 gms of Fe contains 50N/56 atoms

Clearly Aluminum has more number of atoms. This is because Aluminum has a smaller atomic mass and is lighter.