The chemical reactivity of molecular clusters, mainly from the same atom type, is analyzed by using the Fukui function. The Fukui function at each atomic site is estimated from a Hiickel-like approach, based on the variational principle for this reactivity index, where we go beyond the connectivity matrix and introduce a bond-distance dependence in the off-diagonal terms. This approach includes the full set of molecular orbitals with different weights and provides the correct reactivity pattern of the nanoparticle C-360.