  We study prospects for seismic sounding the layer of a partial mixing above
the convective core in main-sequence stars with masses in the 1.2 -- 1.9 solar
mass range. There is an initial tendency to an increase of convective core mass
in such stars and this leads to ambiguities in modeling. Solar-like
oscillations are expected to be excited in such objects. Frequencies of such
oscillations provide diagnostics, which are sensitive to the structure of the
innermost part of the star and they are known as the small separations. We
construct evolutionary models of stars in this mass range assuming various
scenarios for element mixing, which includes formation of element abundance
jumps, as well as semiconvective and overshooting layers. We find that the
three point small separations employing frequencies of radial and dipole modes
provide the best probe of the element distribution above the convective core.
With expected accuracy of frequency measurement from the space experiments, a
discrimination between various scenarios should be possible.
