Normal-mode charge sensitivity analysis, based upon the semiempirical valence-shell hardness tensor in the atoms-in-molecules (AIM) resolution, has been applied to the V 2O 5 surface clusters, ranging from 1 to 6 pyramidal units, with the global number of electrons N corresponding to the net cluster charges (oxidation states) q varying from + 4 to −4. The AIM charges used to model the hardness tensor are from the semiempirical SCF MO calculations in the S (scaled) INDO approximation. The new phase convention for the populational normal modes (directions of the tensor principal axes) is introduced via the requirement φ α. ≡ ∂ N / ∂υ α > 0 for all charge transfer (CT) active modes, where υ α is the collective electron population coordinate associated with the mode α. This convention allows one to identify the modes exhibiting the donor/acceptor behaviour opposite to the global basic/acidic characteristic of the system, as those corresponding to the negative normal Fukui function (FF) index, ⨍ α ≡ ∂υ α / ∂ N < 0, similarly to the familiar AIM description. The q-dependence of the AIM and normal FF indices, as well as that of shapes and selected characteristics of the CT active normal modes, are examined with a special emphasis on the charge instability region, where the principal hardness, h α ≡ ∂μ α/∂υ α, of the softest mode (α = 1) becomes negative and the global hardness η ≡ ∂ 2 E /∂ N 2 < 0; here E denotes the system electronic energy and μ α is the mode chemical potential: μ α ≡ ∂ E/∂υ α. The compared quantities include: h α, φ α, ⨍ α, χ α = −μ α, and the product w α = φ α⨍ α reflecting the mode energy contribution in units of the overall CT energy. The pattern of reactivity indices is shown to be strongly dependent on the cluster oxidation/reduction state.