A systematic study of the mass spectra of particles formed in a supersonic nozzle expansion of Zn, Cd, and Hg vapors together with Na was performed. The particles discussed in this paper contain only 1 heavy atom and <12 Na ligands. Mass spectra from the neutral particles were generated by photoionization at 5 wavelengths (250, 260, 280, 300, and 320 nm) with a slit width corresponding to 16.5 and 3.3 nm, resp. The abundances were cor. to relative differential ionization cross-sections. Photoionization potentials for NanM with 5 < n < 10 and M = Zn, Cd, Hg were measured. Below n = 6, no mixed clusters were found. The 1st abundance max. occurred for all M at n = 8. A 2nd max. was with n = 16 or n = 18. This selectivity can be rationalized by recent ab initio calcns. and by jellium calcns., which give a closed shell at n = 8 with th occupations 1s21p62s2. Ionization potentials clearly show a level reversal to 1p-2s-1d in contrast to the homonuclear jellium with 1p-1d-2s. This is similar to previous results with KnMg. Mol. dynamics simulations with empirical potentials show that the heavy metal migrates to the center of a cube in the frozen asymptote of Na8M. At finite temps. and for larger central atoms, a square antiprismal arrangement seems to be more stable. [on SciFinder (R)]