This prediction might have some significant consequences in the definition and detection of HPEs: if the sharp increase of the atomic electronegativity of an element, due to the formation of a MCB, is a signature of the transition towards an electride state, it might be possible to experimentally characterize a HPE by probing the binding energies of the valence states of the element before and after the transition. This is a hypothesis that we will explore in future studies. Moreover, this orbital hybridization would also have some interesting implications on the redox reactivity of Ca at HP, since Ca, in its sc phase, becomes more electronegative then zirconium, yttrium or titanium at the same pressure (considering the HP values of the isolated atoms for Zr, Y and Ti), suggesting a possible electronegativity inversion of Ca with these elements at high-pressures.