# Dispersion in Chromatography Columns - The Random Walk Model > Page 8

Lateral Movement/Particle =

It follows, that the average lateral step will be,

Employing the random walk function, the radial variance will be given by:- (2)

Now assuming one lateral step is
taken by a molecule for every distance (jd_{p}) that it moves axially,
then, (n) the number of steps is given
by:-
_{}

where (l) is the distance traveled axially by the solute band.

Thus, substituting for (n) in equation (2),