The distribution of elements in galaxies provides a wealth of information about their production sites and their subsequent mixing into the interstellar medium . Here we investigate the elemental distributions of stars in the IllustrisTNG simulations . We analyze the abundance ratios of magnesium and europium in Milky Way-like galaxies from the TNG100 simulation ( stellar masses { \log } ( M _ { \star } / { M } _ { \odot } ) \sim 9.7 - 11.2 ) . Comparison of observed magnesium and europium for individual stars in the Milky Way with the stellar abundances in our more than 850 Milky Way-like galaxies provides stringent constraints on our chemical evolutionary methods . Here , we use the magnesium to iron ratio as a proxy for the effects of our SNII and SNIa metal return prescription and as a comparison to a variety of galactic observations . The europium-to-iron ratio tracks the rare ejecta from neutron star – neutron star mergers , the assumed primary site of europium production in our models , and is a sensitive probe of the effects of metal diffusion within the gas in our simulations . We find that europium abundances in Milky Way-like galaxies show no correlation with assembly history , present day galactic properties , and average galactic stellar population age . We reproduce the europium-to-iron spread at low metallicities observed in the Milky Way , and find it is sensitive to gas properties during redshifts z \approx 2 - 4 . We show that while the overall normalization of [ Eu/Fe ] is susceptible to resolution and post-processing assumptions , the relatively large spread of [ Eu/Fe ] at low [ Fe/H ] when compared to that at high [ Fe/H ] is quite robust .