A particle is defined as a small potion of matter. From its definition, then a single atom can be considered as an atom. This is because an atom is the smallest unit of matter. Also, a molecule can be considered as a particles since it is a small portion of a certain object.
Van der Waals forces include attractive forces arising from interactions between the partial electric charges and repulsive forces arising from the Pauli exclusion principle and the exclusion of electrons in overlapping orbitals.
60+68=128
128/2=64
so the answer is 64
I hope this helped