High-precision abundances of elements have been derived from HARPS-N spectra of F and G main-sequence stars having ages determined from oscillation frequencies delivered by the Kepler mission. The tight relations between abundance ratios of refractory elements, e.g., [Mg/Fe] and [Y/Mg], and stellar age previously found for solar twin stars are confirmed. These relations provide new information on nucleosynthesis and Galactic evolution. Abundance ratios between volatile and refractory elements, e.g., [C/Fe] and [O/Fe], show on the other hand a significant scatter at a given age, which may be related to planet-star interactions. This is a potential problem for chemical tagging studies.