Adapted from Supplementary Fig. 5 of Dunk et al. (2014). Behaviour of the chemical elements for the formation of mono-atom endohedral compounds with C₆₀: grey-blue squares, elements that form mono-metallofullerenes in laser graphite ablation; full yellow squares, elements that do not form confirmed mono-atom endohedral compounds; light blue squares, rare gases that form mono-atom endohedral compounds; yellow squares with grey-blue thick borders, other non metals that form mono-atom endohedral compounds. In addition, a few abundant cosmic elements that do not form confirmed mono-atom endohedral compounds in laser graphite ablation, are indicated by yellow squares with red thick borders.