2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/102261We give a simple characterization of Lie elements in free pre-Lie algebras as elements of the kernel of a map between spaces of trees. We explain how this result is related to natural operations on the Chevalley-Eilenberg complex of a Lie algebra. We also indicate a possible relation to Loday's theory of triplettes.21 pages, LaTeX2e with jltmac2e style. Final version, to appear in Journal of Lie TheoryAlgebraic TopologyK-Theory and Homologytext