Molecular weight of 1 mole of Argon = 39.948 g
for face-centered cube = x = (√8)r and here r = 191 pm
so, x = √8 x 191 = 540 pm = 540 x 10^-10 cm
density = (39.948g / mol) x (unit cell / 540x10^-10 cm)^3 x (mol / 6.022x10^23 atoms) x (4 atoms / unit cell) = 1.69g/cm^3
so density of solid argon is 1.69g/cm^3
