Why there's a difference in mass number between 1 mole of Na and 1 mole Ca?
Size of particles
Size of particles
The size of particles defines how much of matter is contained within and hence, the mass number of substances differ a well. Whenever we consider a huge substance compared with a very minute one, the only difference between the two is their mass. As the particle number in both is same, it's the size of particles which will define the significant difference in mass.