The number of Ar atoms in 40 g (1 mole) =6×1023
⇒ Number of atom in 1.4 g=1.440×6×1023
As density = 1.4 g/mL or 1.4 g/cm3
Number of atoms in 1 cm3 = No. of atoms in 1.4 g=1.440×6×1023 atoms.
Since the volume of each atom is 43πr3 where r = 2.0×10−8cm, we can say volume occupied by atoms
∴ per 1 cm3 of solid 0.704 cm3 volume is occupied by the atoms.
Hence % of empty space =[1−0.704]1×100=29.6