Chemical composition as a function of the interior mass coordinate of a non-rotating model with M_ZAMS = 80 M_⊙ and [Fe/H] = −2 at the pre-SN stage. We report the abundances of H (long dash-double dotted black line), He (double dash-dotted red line), ¹²C (long dashed green line), ¹⁶O (short dashed blue line), ²⁰Ne (dashed magenta line), ²⁸Si (short dash-double dotted orange line), ⁵²Cr (solid dark red line) and ⁵⁶Fe (long dash-dotted gray line).