The use of electronegativity as a resource is not surprising for OC1 students because 355 these arguments explain the differences in chemical shift for halogenated molecules such as CH3F or CH3Cl. Electronegativity is used to explain how electron density surrounding protons can be depleted, which results in an increase in chemical shift. As a resource, electronegativity is used to a lesser extent in OC2, particularly with aromatic molecules with resonance structures used to account for the reactivity and regioselectivity of aromatic rings.