The edge feature matrix is used to represent the bond properties including not only the bond type (single, aromatic, double, and triple bond) but also conjugation and bond polarization. Polarization is computed as the difference in electronegativity between the atoms making up each bond. To ensure the impact of this polarization on the ionization center is considered, the polarization should be directed (donating or withdrawing). To account for this direction, the polarization is computed as the difference between the atom the further away and the one closer from the ionization center. These features are expected to model resonance and inductive effects.