Use is made of the fact that the NMR Knight shift K can be used as a local, i.e. atomic scale, indicator of whether the electronic state of the atom is metallic or non-metallic. The authors have measured K for the probe atom Bi in the liquid semiconductor system Tl-Te, and find that K_Bi drops in a narrower range around Tl₂Te than either K_Te or the susceptibility. Adopting the quasichemical model for the analysis, it is concluded for this system that a Bi atom needs only a very small number of metallic neighbours (either Tl or Te) in order to show the metallic value of K.