Surface state experimental data is shown to agree with recent theories developed for the large bandgap ionic and partially ionic crystals. The surface states appear in pairs. An acceptor-like surface state band lies generally a few tenths of an eV below the conduction band, and a donor-like surface state band generally lies a few tenths of an eV above the valence band. The surface state bands merge with the corresponding conduction and valence bands. The smaller the bandgap Eg of the compound, the closer the states move towards midgap, provided Eg>1 eV. Furthermore, for n-type samples the bands bend up at the surface, while for p-type samples the bands bend down. But for Eg<1 eV, the surface Fermi level is always located at or near the valence band edge; this may be because these crystals are less ionic.