  High-temperature superconductors are reviewed in light of the fact that their
binding energy is ionic. The conducting electrons are dominated by the much
larger energy scales coming from ligand Coulomb integrals, including the
out-of-plane ones, which are responsible for the Fermi arcs. The historic
reinterpretation of Hund's rule from an intraelectronic to a central mean-field
effect is applied to compare the cuprates to the pnictides. It is argued that
the cuprates conform to the now-standard central-field paradigm, while the
generally abandoned intraelectronic mechanism is exceptionally applicable to
the pnictides. A non-adiabatic Fermi liquid paradigm is inferred from the
phenomenological evidence. Glueless superconductivity is interpreted as the
limiting case of Cooper-pair scattering in cuprates when the Cu ion is
perfectly rigid.
