(i) According to Avogadro’s Law, 1 mole of Argon → 6.023×1023 atoms of Argon So, 52 moles of Argon → X atoms of Argon X =52×6.023×1023 =3.13196×1025 Therefore in 52 moles of Argon 3.13196×1025 atoms are present. (ii) Atomic Mass of Helium [He] = 4 u This means that mass of one atom of Helium is = 4 u So, Number of atom of Helium contained in 52 u = 52/4= 13 atoms Therefore, in 52 u of Helium 13 atoms are present. (iii) Atomic Mass of Helium [He] = 4 u Number of Moles of Helium in 52 g = 52/4= 13 moles So, Number of atoms in 52g of Helium [He] = 13×6.023×1023= 7.8299×1024 Therefore, in 52 g of Helium 7.83×1024 atoms are present.