Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given, atomic mass of Na = 23u, Fe =56 u)?

Atomic mass of Na = 23u   (Given)

Then, gram atomic mass of Na = 23g

Now, 23g of Na contains = 6.022×10²³ number of atoms

Thus, 100g of Na contains = {6.022×10^{23} ×100\over23} number of atoms

= 2.6182 × 10²⁴ number of atoms

Again, atomic mass of Fe = 56u   (Given)

Then, gram atomic mass of Fe = 56g

Now, 56 g of Fe contains = 6.022×10²³ number of atoms

Thus, 100 g of Fe {6.022×10^{23} ×100\over56} number of atoms

= 1.0753 × 10²⁴ number of atoms

Therefore, 100 grams of sodium contain more number of atoms than 100 grams of iron.