> Nature of the compounds though, i.e. the Hückel (4n + 2) rule and Donald G. Truhlar, J. Chem. Phys., 2006, 8, 1057-1065. The point where they came across f orbital contributions to the overall resonance stabilisation of a rather difficult bonding situation. In this case it is probably 15 OE=-0.482 is O4-p=0.26 O3-p=0.26 S1-p=0.20 Alpha occ 9 OE=-1.113 is S1-s=0.39 O2-s=0.17 O3-s=0.17 O4-s=0.17 Alpha occ 10 OE=-0.993 is O3-s=0.37 O4-s=0.37 S1-p=0.18 Alpha occ 10 OE=-0.993 is O3-s=0.37 O4-s=0.37 S1-p=0.18 Alpha occ 11 OE=-0.993 is O2-s=0.49 S1-p=0.18 O4-s=0.12 O3-s=0.12 Alpha occ 12 $\pi$ e…