This research is aimed to propose and evaluate a didactic sequence for the introduction of algebraic activity in elementary school (2nd grade). This sequence was composed by five interconnected modules, addressing aspects considered central in the conceptual field of algebra, like identification and modeling of transformations, symbolic representation, manipulation of relations of difference and equality, and manipulation of unknown quantities symbolically represented. Results show the possibility of introducing this kind of mathematical activity since very early, in parallel with arithmetics, provided that the passage from the manipulation of known to unknown quantities is firstly based on natural language and preceded by preparatory activities, and the literal representation of unknowns carefully assisted.