State which has higher no. of atoms : 1 g of O₂ or 1 g of Cl₂ [O = 16, Cl = 35.5]

Molecular mass of O₂ = 2 x 16 = 32 g

32 g of O₂ = 2 x 6.023 x 10²³ atoms

∴ 1 g of O₂

$= \dfrac{2 \times 6.023 \times 10^{23}}{32} \\[0.5em] = 0.0625 \times 6.023 \times 10^{23} \text{ atoms}$

Molecular mass of Cl₂ = 2 x 35.5 = 71 g

71 g of Cl₂ = 2 x 6.023 x 10²³ atoms

∴ 1 g of Cl₂

$= \dfrac{2 \times 6.023 \times 10^{23}}{71} \\[0.5em] = 0.0281 \times 6.023 \times 10^{23} \text{ atoms}$

Hence, 1 g of O₂ has more number of atoms.