[J_Jhonna_Jhonson]

I was looking for the derivation of the formula of Van der wall’s constant b=4×v_1molecule on Wikipedia https://en.m.wikipedia.org/wiki/Van_der_Waals_equation

I understood it all except the last part of dividing by 2. Why do we require to divide by 2? We just require the excluded volume, which is the volume where centers of the molecules can’t reach, which gives b=8×V_1molecule .

What is the reasoning for dividing by 2?

[MNIO]

b is excluded volume PER PARTICLE and there are two particles in that analysis