The overall nuclear-spin Hamilton operator for a solid is typically expressed as a sum of Hamilton operators, yet herein we focus on just one of those Hamiltonians, chemical shielding, and in particular the differing chemical shielding between free and adsorbed ethylene. In the absence of unpaired electronic spins, two effects contribute to the chemical shift and have the potential to impact the characteristic features of the C NMR spectrum of ethylene adsorbed on different substrates. Firstly, the motion of electrons within their orbitals generates magnetic fields that oppose the direction of the external 𝐵𝐵0 field according to the Lenz-rule. This reduces the effective magnetic field at the site of the nucleus in the form of a diamagnetic effect. Secondly, the admixture of excited electronic states contributes further angular momenta to electrons that can produce a paramagnetic deshielding effect. These diamagnetic and paramagnetic effects must be examined in the context of local fields at the nucleus.