The present work is focused on parametric computations of electron energy distribution function (EEDF) and electron mobility in resonant photo-plasma of sodium mixed
with argon and molecular nitrogen. The conditions of a weak external electric field are considered, when electron heating is provided by collisions of the second kind with excited sodium atoms. It is shown that the non-equilibrium shape of the EEDF arising in this mixture can considerably affect electron mobility. It is demonstrated that under certain conditions the mobility may have negative values. The critical plasma parameters (partial pressure of mixture
components, plasma ionisation degree (ξ), population of excited sodium atoms, electric reduced field strength, vibration temperature of nitrogen molecules) are elucidated.