The radius of an argon atom is about 0.19 nm.
(a) Estimate the mean free path of argon atoms at a pressure of 1 Atm and T = 273K.  Compare your result with the radius and with the typical distance, L, between atoms.  This last quantity can be found by taking the cube root of the volume occupied by each atom.
(b) Find the RMS distance that the atoms diffuse along the x axis in a time of 10 seconds.  Compare the result with the total distance travelled by the atom (i.e., the distance measured along the atoms path) during this time.