The purpose of this study is the assessment of the properties of the conductance of silicon nanostructures. The calculation method, taken from the recent chemical literature, is based on the scattering approach and on the extended Hückel theory and is further simplified by the parametrization of the contact potentials in terms of the Hamiltonian of the active region. The structures considered are crystalline columnar grains sandwiched between two adsorbing contacts and their size reaches 400 atoms. The calculations analyse the structural parameters and the electronic configuration of the grains and examine the relationship between this quantity and the conductance. It is shown that the conductance depends on the energy difference across the occupied energy levels and for this reason has the same dependence on the grain size and shape as the binding energy. This allows an unified formulation of the electronic …