  In this work we present a study of the strong optical collisional emission
lines of Ne and Ar in an heterogeneous sample of ionized gaseous nebulae for
which it is possible to derive directly the electron temperature and hence the
chemical abundances of neon and argon. We calculate using a grid of
photoionization models new ionization correction factors for these two elements
and we study the behaviour of Ne/O and Ar/O abundance ratios with metallicity.
We find a constant value for Ne/O, while there seems to be some evidence for
the existence of negative radial gradients of Ar/O over the disks of some
nearby spirals. We study the relation between the intensities of the emission
lines of [NeIII] at 3869 \AA and [OIII] at 4959 \AA and 5007 \AA. This relation
can be used in empirical calibrations and diagnostic ratios extending their
applicability to bluer wavelengths and therefore to samples of objects at
higher redshifts. Finally, we propose a new diagnostic using [OII], [NeIII] and
Hdelta emission lines to derive metallicities for galaxies at high z.
