[X/Fe] versus [Fe/H] relations for sodium (panel a), aluminium (panel b) and potassium (panel c) in the solar neighbourhood. Theoretical predictions are from Models 1 [short-dashed (red) lines], 4 [upper solid (blue) lines], and 5 [lower solid (black) lines]. Data are from Andrievsky et al. (2007, 2008, 2010, stars, for Na, Al, and K, respectively), Lai et al. (2008, open pentagons), Gratton et al. (2003, upside-down triangles), Gehren et al. (2006, open triangles), Zhang et al. (2006, open circles), Reddy et al. (2006, filled squares), Reddy et al. (2003, open squares), and Bensby et al. (2005, filled circles). LTE abundances from Lai et al. (2008) have been corrected by  − 0.5 dex for Na (Baumüller et al. 1998) and +0.65 dex for Al (Baumüller & Gehren 1997). See the electronic edition of the journal for a colour version of this figure.